SEARCH

SEARCH BY CITATION

Keywords:

  • Araripe Basin;
  • Brazil;
  • Early Cretaceous;
  • eusuchian evolution;
  • postcranial anatomy

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GEOLOGICAL SETTING
  5. SYSTEMATIC PALEONTOLOGY
  6. DESCRIPTION
  7. DISCUSSION
  8. ACKNOWLEDGEMENTS
  9. REFERENCES
  10. Appendices

A third specimen of Susisuchus anatoceps is described. The new material comprises postcranial remains, including an almost complete sequence of cervical vertebrae, prothoracic and posterior dorsal vertebrae, and osteoderms from dorsal and ventral shield, scapula, coracoid and the forelimb. The new specimen (MPSC-R1136) was recovered from the Crato Formation (Lower Cretaceous) of the Santana Group, near Nova Olinda municipality, Ceará State, Brazil. Some cervical vertebrae show slightly procoelous centra and at least one of these vertebrae is platycoelic, a feature reported for the first time in Susisuchus. Nevertheless, dorsals have amphicoelic centra. The sagittal segmented dorsal shield comprises two paravertebral rows of square osteoderms and two accessory rows of ellipsoidal osteoderms on each side of the trunk. Three diagnostic characters are present in the new Susisuchus specimen: the proximal and distal articulations of the ulna have about the same width and are thicker with respect to the shaft; the scapular blade has posterior concave and anterior straight margins; and the ungual phalanges are present only on first and second digits of the manus. A phylogenetic analysis of Susisuchus anatoceps based on new characters of MPSC-R1136 in addition to the holotype, and employing a previous data set of Jouve, placed this taxon as a basal member of the advanced neosuchian clade.

© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S273–S288.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GEOLOGICAL SETTING
  5. SYSTEMATIC PALEONTOLOGY
  6. DESCRIPTION
  7. DISCUSSION
  8. ACKNOWLEDGEMENTS
  9. REFERENCES
  10. Appendices

The fossil assemblage of the Santana Group (Aptian–Albian; Pons, Berthou & Campos, 1990) is one of the most famous and diverse from South America: it consists of two Lagerstätten with vertebrate remains known from both the Crato and Romualdo Formations (for a review see Maisey, 1991; Kellner & Campos, 1999). Three crocodylomorphs have been formally described: Araripesuchus gomesii, Caririsuchus camposi, and Susisuchus anatoceps (Price, 1959; Kellner, 1987; Hecht, 1991; Salisbury et al., 2003). The existence of ten other specimens were mentioned by Frey & Salisbury (2007), but they do not provide information on which elements are preserved or on the provenence of material and, as far as we know, they are not available for scientific study at present.

New discoveries from South America and Australia suggest that a relevant part of the evolutionary history of Neosuchia, particularly the eusuchian lineage (including the crown-group Crocodylia and all living forms), took place in Gondwana during Cretaceous times (Salisbury et al., 2003, 2006). The small advanced neosuchian Susisuchus anatoceps, presently regarded as lying outside the Eusuchia, has key postcranial anatomical characteristics associated with the transition from the neosuchian to the eusuchian bauplan.

Here we present a third specimen of Susisuchus anatoceps (MPSC-R1136) that provides new important anatomical information for this taxon. This exemplar was recovered from a quarry near Nova Olinda municipality, Ceará State, Brazil.

Abbreviations

Institutional: MN-UFRJ, Museu Nacional, UFRJ, Rio de Janeiro, Brazil; MPSC, Museu de Paleontologia de Santana do Cariri, Brazil; SMNK, Staaliches Museum für Naturkunde Kalsruhe, Germany.

Anatomical: ax, axis; c3, cervical vertebra 3; c4, cervical vertebra 4; c5, cervical vertebra 5; c6, cervical vertebra 6; c7, cervical vertebra 7; c8, cervical vertebra 8; dg, digit; dr, dorsal rib; dv, dorsal vertebra; lac, lateral accessory osteoderm; mac, medial accessory osteoderm; pav, paravertebral osteoderm; rad, radius; uln, ulna; vos, ventral osteoderm.

GEOLOGICAL SETTING

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GEOLOGICAL SETTING
  5. SYSTEMATIC PALEONTOLOGY
  6. DESCRIPTION
  7. DISCUSSION
  8. ACKNOWLEDGEMENTS
  9. REFERENCES
  10. Appendices

The Araripe Basin is located in northeastern Brazil, covering parts of Ceará, Piauí and Pernambuco states. The origin of this basin is directly related to the opening of the South Atlantic Rift System, but the deposition of the Santana Group occurred only in the post-rift stage (Ponte & Ponte Filho, 1996). Although the stratigraphic nomenclature is disputed (e.g. Beurlen, 1963, 1971; Brito-Neves, 1990; Assine, 1992; Ponte & Ponte Filho, 1996; Neumann & Cabrera, 1999) we follow Neumann & Cabrera (1999).

The Lagerstätten of the Crato and Santana Formations are the most relevant from the palaeontological aspect and these strata are regarded as Aptian/Albian and Albian, respectively (Pons et al., 1990). The lithostratigraphy of the Crato Formation represents a sequence of deltaic to lacustrine sediments (i.e. a palaeolake with fluvial outflows) with a constant calcareous depocentre (Neumann & Cabrera, 2002), which is confirmed by several elements of the preserved biota (Kellner, 1994; Kellner, Maisey & Campos, 1994). Lithologicaly this stratigraphic unit is formed by a pelitic–calcareous section essentially of laminated limestones that comprises six carbonatic units (C1–C6) separated from one another by sandstones, siltstones, and mudstones (Assine, 1992).

Neumann & Cabrera (2002) recognize several transgression and regression episodes within the Araripe lacustrial system: during the regression phases intake of water and sediments was diminished, causing a subsequent increase in salinity. The periodic rises in the salinity of the Crato Formation palaeolake were probably a limiting factor for the biota, although lasting freshwater intake was present in regions near the fluvial–deltaic outflows, maintaining a halocline (Neumann & Cabrera, 2002).

SYSTEMATIC PALEONTOLOGY

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GEOLOGICAL SETTING
  5. SYSTEMATIC PALEONTOLOGY
  6. DESCRIPTION
  7. DISCUSSION
  8. ACKNOWLEDGEMENTS
  9. REFERENCES
  10. Appendices

CrocodylomorphaWalker, 1970

Crocodyliformes Hay 1930 (sensuBenton & Clark, 1988)

Susisuchus anatocepsSalisburyetal., 2003

Holotype: SMNK 3804 PAL – an incomplete partially articulated skeleton, comprising the skull and mandible; cervical, dorsal, sacral, and caudal vertebrae; pectoral girdle including the right and left forelimbs and osteoderms from the nuchal and dorsal shield (Salisbury et al., 2003). Cast at the Museu Nacional/UFRJ (MN 6924-V), Rio de Janeiro.

Referred specimens: MPSC-R1136 – partially articulated postcranial remains comprising cervical and dorsal vertebrae; bones of the pectoral girdle including the right forelimb; and osteoderms from the dorsal shield. MPSC-R1137 – a complete partially articulated right hind limb, including femur, tibia, fibula, and pes (Figueiredo & Kellner, 2009).

Emended diagnosis: Susisuchus anatoceps differs from other crocodylomorph taxa based on the following combination of osteological features (autapomorphic characters marked with an asterisk): posterior process of the maxillary bone separating the lacrimal from nasal; lacrimal extends anteriorly beyond the anterior limit of the prefrontal; teeth needle-like and homodont; 11 thoracic vertebrae; four lumbar vertebrae; minimum width of the sacral ribs in an anteroposterior direction exceeds the maximum width of any of the diapophyses; postzygapophyses of caudal vertebrae 6–11 (the vertebrae terminal to caudal 11 are not preserved) unite medially to form a flat, horizontally aligned shelf, which extends terminally over the vertebral foramen; *maximum width of the proximal extremity of the ulna equivalent to that of the distal extremity, and about twice the minimum thickness of the ulnar shaft; absence of an anterior tubercle on the proximal extremity of the ulna; *unguals present only in hand digits 1 and 2; *scapular blade has straight anterior margins and concave posterior margins; dorsal shield comprising two rows of paravertebral osteoderms and two left and two right rows of accessory scutes; procoelous cervical vertebrae and platycoelous last cervical vertebra; amphicoelous thoracic, lumbar, and caudal vertebrae.

DESCRIPTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GEOLOGICAL SETTING
  5. SYSTEMATIC PALEONTOLOGY
  6. DESCRIPTION
  7. DISCUSSION
  8. ACKNOWLEDGEMENTS
  9. REFERENCES
  10. Appendices

General

Specimen MPSC-R1136 comprises postcranial remains of a small neosuchian crocodylomorph preserved on a limestone plate typical of the Crato Formation (Figs 1, 2). The anterior dorsal vertebrae are preserved followed by the dorsal shield osteoderms. Posterior to the dermal skeleton are the last vertebrae of the dorsal series. Bones of the right forelimb are also present: the ulna, the radius, and the manus. The humerus, the scapula, and the coracoid were removed from the limestone matrix after mechanical and chemical prepared with acid. An almost complete sequence of cervical vertebrae in articulation with the ribs were also prepared and removed from the slab.

image

Figure 1. Dorsal vertebrae, dorsal shield, and forelimb (zeugapodial elements and manus) of Susisuchus anatoceps (MPSC-R1136). Abbreviations: dg1–3, digits 1–3; dr1–4, dorsal ribs 1–4; dv7–10, dorsal vertebrae 7–10; lac, lateral accessory osteoderm; mac, medial accessory osteoderm; pav, paravertebral osteoderm; rad, radius; uln, ulna; vos, ventral osteoderms. Scale bar = 30 mm.

Download figure to PowerPoint

image

Figure 2. Drawing of the dorsal vertebrae, dorsal shield, and forelimb (zeugapodial elements and manus) of Susisuchus anatoceps (MPSC-R1136). Scale bar = 30 mm.

Download figure to PowerPoint

No great taphonomic deformation is perceptible on most of the specimen, although the left surface of the cervical vertebrae (preserved facing down on the matrix) is slightly damaged and the ribs are broken. The ulna and radius also show some fractures along their shafts and only the broken coracoid articular surface with scapula is preserved. MPSC-R1136 is housed at the Museu de Paleontologia de Santana do Cariri (MPSC) from Universidade Regional do Cariri (URCA) and a cast has been deposited at the Paleovertebrate Sector collection of Museu Nacional/UFRJ under number MN 6924-V.

Axial skeleton

Cervical vertebrae

The cervical sequence comprises seven vertebrae from axis to cervical 8 and also a small trapezoidal-shaped bone associated with the axis, which we tentatively regard as the atlas intercentrum (Fig. 3). The axis is elongated and has the centrum longer than higher. The anterior portion of the neural arch and the neural spine are slightly damaged. Axial postzygapophyses are short in comparison with those from the posterior vertebrae. The axial centrum is cylindrical in ventral view and shows neither parapophyses nor hypapophysis. The absence of axial hypapophyses is atypical in neosuchians and eusuchians; they are present in Bernissartia, Theriosuchus, and Isisfordia and usually they are prominent in extant species (Brochu, 1999; Salisbury et al., 2006). Nevertheless, the lack of diapophyses is much more common in Neosuchia (including eusuchians; exceptions include Bernissartia and Gavialis) (Brochu, 1999). Unfortunately the axis is not preserved in the holotype of Susisuchus anatoceps (Salisbury et al., 2003).

image

Figure 3. Cervical vertebrae of Susisuchus anatoceps (MPSC-R1136). A, ventral view showing the poorly developed hypapophyses. B, lateral view showing the neural spines. Abbreviations: ax, axis; c3–8, cervical vertebrae 3–8. White arrows indicate the neural spines. Scale bars = 10 mm.

Download figure to PowerPoint

The postaxial cervical vertebrae are higher than longer and they slightly increase in stoutness on approaching the posterior end of the neck. These vertebrae show well-developed diapophyses and parapophyses of essentially the same size. These processes are lateroventrally directed and have a gap between them, which is marked by the narrowing of the tuberculum and capitulum of the cervical ribs.

The neural spines are located posteriorly on the neural arch and all are laminar of about the same width, contrary to what was reported for Susisuchus anatoceps by Salisbury et al. (2003). This uniformity in neural spines width is also seen in Goniopholis, Isisfordia, and Gavialis (Brochu, 1997, 1999; Salisbury et al., 2006). The total height of the neural spines cannot be determined.

The first postaxial vertebra has a weakly developed hypapophysis, which is the general condition for most neosuchian taxa (e.g. Bernissartia, Theriosuchus) and also for Isisfordia duncani. Extant crocodylomorphs have prominent hypapophyses in first postaxial cervical vertebrae, except Gavialis gangeticus (Brochu, 1997, 1999).

All hypapophyses of MPSC-R1136 are poorly developed in comparison with living taxa. In the posterior vertebrae, these structures are keel-shaped, without any forking, running anteroposteriorly in the ventral surface of the centrum. There is no information available regarding the cervical hypapophyses of the holotype of Susisuchus; nevertheless in other neosuchians such as Theriosuchus guimarotae and Pachycheilosuchus trinquei they are knob-like (Rogers, 2003; Schwarz & Salisbury, 2005).

At least the axis and the third, sixth, and seventh vertebrae have slightly procoelous centra (Fig. 4), which are very similar to Isisfordia vertebrae but rather different from the amphicoelic condition described for the holotype of Susisuchus anatoceps (Salisbury et al., 2006). Another taxon that shows an unequal arrangement of the cervical vertebrae articular surfaces is Pachycheilosuchus trinquei from the Glen Rose Formation (Albian) of Texas (Rogers, 2003). However, this taxon can be distinguished from Susisuchus by the presence of a secondary ossified plug that is present in the vertebrae of the North American species. This seems to be a unique and therefore diagnostic trait for Pachycheilosuchus.

image

Figure 4. Detail of the sixth cervical vertebrae of Susisuchus anatoceps (MPSC-R1136). The arrow indicates the procoelic end of the vertebra centrum. Scale bar = 5 mm.

Download figure to PowerPoint

The eighth cervical vertebra is quite different from the other cervicals. The diapophysis and parapophysis are considerably smaller and the thin and sharp keel-like hypapophysis is more developed. Although the eighth vertebra is deformed, in posterior view it is possible to observe the slightly flat end of the centrum, indicating platycoely in this specific vertebra. Theriosuchus and Susisuchus (MPSC-R1136) are two of the few neosuchians that have two types of articular posterior ends in cervical vertebrae.

Dorsal vertebrae

The first thoracic vertebrae are preserved in articulation and except for dorsal 1 all other prothoracic vertebrae are overlapped by osteoderms (Figs 1, 2). Many features of the first dorsal resemble those from the last cervical vertebra: the vertebral fossa have a subcircular outline; vertebral foramina are wider than dorsoventrally higher; they have poorly developed parapophyses in comparison with those from anterior cervical vertebrae; and their diapophyses are placed just below the zygapophysial plane. The hypapophysis on dorsal 1 is not thin and keel-like but instead it has a strong and rounded knob shape, as in Pachycheilosuchus (Rogers, 2003).

There are at least six vertebrae preserved after the dorsal shield, all of them displaced from the anatomical position and overlapping each other, which suggests intense decay processes prior to burial. We tentatively interpret the first of them as the seventh dorsal vertebra. The transverse processes of dorsals 7, 8, and 9 are very wide, laminar, and dorsoventrally low, as in extant crocodylians. In general the zygapophyses of posterior dorsal vertebrae are relatively small and rectangular. The tenth dorsal is preserved with its anterior plane facing up, revealing the subcircular vertebral fossa in the centrum. In thoracic 11 it is possible to observe the neural arch with subcircular prezygapophyses and narrow transverse processes in comparison with dorsals 7, 8, and 9. This vertebra has its anterior face directed to the posterior region of the trunk. The 12th vertebra has a spool-shaped centrum with shallow concave posterior end, and is therefore amphicoelic. This is the plesiomorphic condition for Crocodylomorpha, and thus common for most neosuchians as Theriosuchus, Goniopholis, Bernissartia, and the holotype of Susisuchus anatoceps (Benton & Clark, 1988; Norell & Clark, 1990; Salisbury et al., 2003, 2006). Its postzygapophyses are slightly rounded and the transverse processes are similar to those on thoracic vertebra 11.

Cervical ribs

Axial ribs are distinct from other cervical ribs: they have a Y shape, the proximal articular head is much wider than the flat shaft, and the tuberculum and capitulum have rounded articular surfaces. The wide tuberculum of the axial ribs is also found in the two Susisuchus specimens (holotype and MPSC-R1136) and is shared with Theriosuchus and Gavialis (Salisbury et al., 2003, 2006). Ribs 3–7 are very similar to each other, consisting of a stout horizontal shaft with the tubercular and the capitular processes extending perpendicularly from it to meet the vertebrae parapophyses and diapophyses. MPSC-R1136 has a conspicuous flattening in the shaft of ribs 3–7, as described by Salisbury et al. (2003) for the first cervical ribs of the holotype of Susisuchus anatoceps. The last cervical rib differs from others in shape: it is long, straight, and flat with triangular distal extremity. The tuberculum and the capitulum are about the same size but the former is thicker. There is a slight constriction in the base of the articular processes, regarded as the anterior fossa. It is bordered by a small process located medially in the rib shaft. This rib resembles the posterior cervical ribs of extant taxa but it is less arched and more robust (Mook, 1921).

Thoracic ribs

Few thoracic ribs are fully preserved, which includes the first two from the right side and two other posterior ribs. Ribs 1 and 2 are similar to each other and to the last cervical rib. The first rib has a well-developed laminar anterior process. Major differences can be seen in the second thoracic rib, which is larger and has a well-marked convex anteroventral margin. Its anterior fossa is deep. These first ribs are much less curved than those of extant crocodylians and their tuberculum and capitulum are less developed (Mook, 1921). Fragments of the proximal head of ribs 3 and 4 reveal the lack of the tuberculum, which in Crocodylus is absent only posterior to dorsal rib 3 (Mook, 1921). The posterior thoracic ribs are long and greatly curved, similar to the ribs of extant crocodylians, which lack the tuberculum and have distinct capitular and tubercular facets. These ribs have a conservative morphology and are very similar to those of the holotype of Susisuchus anatoceps (Salisbury et al., 2003).

Appendicular skeleton

Scapula and coracoid

The scapular blade is not symmetrical: the posterior margin is slightly concave, while the anterior edge is very thin and straight (Fig. 5). This trait can be seen in the holotype of Susisuchus anatoceps (Salisbury et al., 2003: fig. 2) and is a diagnostic feature of the species. The sharp dorsal border is anteroposteriorly wide with concave outline in lateral view. These features are also present in the holotype of Susisuchus (Salisbury et al., 2003). Anteriorly to the glenoid fossa the scapulocoracoid facet is broad and tapers toward the anterior edge, similarly to Alligator, Caiman, and Crocodylus (Brochu, 1997, 1999); however, this feature is unknown in the holotype of Susisuchus and closely related species such as Isisfordia and Bernissartia (Salisbury et al., 2003, 2006). On the lateral surface of the scapular blade there is a ridge that borders the anteroventral margin, extending dorsally through the middle of the shaft.

image

Figure 5. Shoulder girdle of Susisuchus anatoceps (MPSC-R1136). A, lateral view of the right scapula. B, medial view of the right scapula. C, lateral view of the right coracoid. D, medial view of the right coracoid. Scale bars = 10 mm.

Download figure to PowerPoint

The coracoid shaft is not fully preserved, remaining only its proximal articulation. Nevertheless, this fragment corresponds to approximately 56% of the scapular length. This proportion suggests that these bones could be subequal in length. The glenoid articular facet is larger in coracoids than in the scapula and consists of a rounded posteriorly directed process. The coracoid foramen is large and oval and is visible in medial and lateral views. It is located near the dorsal edge, slightly posteriorly directed.

Humerus

The humerus has typical crocodylomorphan morphology: it is a relatively stout bone with concave medial outline and almost straight lateral margin. In lateral view it is possible to observe that the proximal head is offset by about 20° from the long axis (Fig. 6). The proximal and distal articulations have similar width, about twice as thicker than the midshaft, as known in the holotype of Susisuchus anatoceps (Salisbury et al., 2003). The articular facet for the radius is more developed in MPSC-R1136 than in Pachycheilosuchus (Rogers, 2003).

image

Figure 6. Right humerus of Susisuchus anatoceps (MPSC-R1136). A, anterior view; B, posterior view; C, lateral view; D, medial view. Scale bars = 10 mm.

Download figure to PowerPoint

The deltoid crest is highly developed, located next to the proximal articulation, although in some neosuchians (e.g. Pachycheilosuchus) the gap between the deltoid crest and the proximal articular surface is smaller (Rogers, 2003). It emerges gradually from the shaft, tapering anteriorly and is slightly deflected to the medial line – this feature is also observed in the holotype of Susisuchus (Salisbury et al., 2003). In recent species, however, the deltapectoral typically emerges abruptly, which is characteristic of more derived eusuchians, with the exception of Gavialis (Brochu, 1997, 1999). There is a pronounced ridge with a rugose area bordering the deltoid crest, located lateroposteriorly on the humerus. This is regarded as an insertion scar of the common tendon of both the teres major muscle and latissimus dorsi muscle, in the same way as observed in extant crocodylomorphs (Meers, 2003).

Ulna

The ulna shaft is curved, with a caudally convex surface and uniform width down to the distal end of the bone (Fig. 7). In lateral view the proximal articulation is much wider than the axis, being more than twice as broad in dorsoventral direction. The proportions of proximal and distal ulnar articulations are less discrepant in lateromedial width; the distal extremity of the ulna is about 81% of the proximal end. The small difference in width between the proximal and distal ends of the ulna is only known in Susisuchus anatoceps (regarded as a diagnostic feature), Theriosuchus pusillus, Borealosuchus formidabilis, and Isisfordia duncani (Salisbury et al., 2003, 2006). The total length of the ulna is about 77% that of the humerus. The proximal head has a rounded-triangle shape but the shaft becomes more ellipsoidal in mid-session due a dorsoventral compression. Distally the ulna gradually becomes more triangular again.

image

Figure 7. Detail of the hand bones (zeugapodial elements and manus) of Susisuchus anatoceps (MPSC-R1136). Abbreviations: dg1–3, digits 1–3; rad, radius; uln, ulna. Scale bar = 20 mm.

Download figure to PowerPoint

Radius

The radius is a slender bone and has general shape, size, and proportions that are very similar to that found on the holotype of Susisuchus anatoceps (Fig. 7). The near straight shaft has total length about 86% of the ulna and 66% of the humerus and the minimum thickness of the axis is about 10% of the radius proximodistally length. The proximal articulations in both specimens are about twice as wide as the minimum thickness of the radius (Salisbury et al., 2003). As in the ulna, the radius axis has a dorsoventrally compression that gives it an elliptical shape in cross-section, which is more rounded in the holotype of Susisuchus (Salisbury et al., 2003). The radius head is subcircular in shape in proximal view while its distal end is more triangular. The shaft is smooth and there are no scars, grooves or ridges that can be properly distinguished in this bone; nevertheless some striations can be observed on both the proximal and the distal ends.

Manus

The bones of the manus are preserved close to their original anatomical positions, although digits 4 and 5 are missing (Fig. 7). The carpal radiale, ulnare, and pisiforme bones are present and can be observed in dorsal view along with metacarpals and phalanges of digits 1, 2, and 3. The radiale is the largest and most robust of the carpal bones. It is longer than wider and has asymmetrical articulations: the proximal one projects itself medially more acutely. The ulnare is an hourglass-shaped bone that is approximately 65.5% of the radial carpal length. The metacarpal on the first digit is about half the length of metacarpals 2 and 3 but is much stouter in build. The phalangeal formula (without the unguals) is 1:2:3:?:? from the first to fifth digits. Claws are present only on digits 1 and 2 and both of them are relatively long and slightly curved; this is a unique trait of Susisuchus anatoceps (Salisbury et al., 2003).

Osteoderms

The dorsal shield comprises six longitudinal rows of osteoderms, formed by two medial rows of paravertebral osteoderms plus two rows of accessory osteoderms located on each side of the trunk (Figs 2, 8). In the prothoracic region most of the osteoderms are superimposed, making it difficult to determinate the total number of elements and the number of transverse rows in this specimen.

image

Figure 8. Detail of the dorsal shield of Susisuchus anatoceps (MPSC-R1136) showing the six contiguous rows (white triangles) of osteoderms. Scale bar = 5 mm.

Download figure to PowerPoint

The paravertebral series consists of square osteoderms with strongly sculptured external surfaces that are divided into medial and lateral halves by dorsally tapering keels. The anterior osteoderms are slightly longer than wide and comparatively smaller in size than those of the posterior end. The medial borders of the paravertebral osteoderms are straight but the lateral borders are convex with gentle dentate margins.

Accessory osteoderms are ellipsoidal and those from the medial rows are larger than those from the lateral rows. As in the paravertebral shield, the accessory osteoderms have their external surface strongly sculptured by subcircular pits. The longitudinal keels, which also separate these osteoderms in medial and lateral sides, are proportionally higher than those on larger osteoderms.

The ventral osteoderms were preserved from both posterior and anterior regions of the shield showing their internal (dorsal) surface, where a few vascular pits and crossed grooves can be observed. There are large square and smaller ellipsoidal osteoderms, resembling the morphology of those found on the dorsal shield.

The presence of two paravertebral rows of osteoderms in Susisuchus anatoceps (reinterpreted based on MPSC-R1136) is consistent with other advanced neosuchians such as the ‘Las Hoyas neosuchian’, which also have lateral accessory osteoderms (Salisbury & Frey, 2001). Recent eusuchians normally have six to eight rows of osteoderms, although Gavialis shows only four (Brochu, 1999).

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GEOLOGICAL SETTING
  5. SYSTEMATIC PALEONTOLOGY
  6. DESCRIPTION
  7. DISCUSSION
  8. ACKNOWLEDGEMENTS
  9. REFERENCES
  10. Appendices

The Cretaceous deposits from Brazil have provided several crocodylomorph remains, especially notosuchians, sphagesaurids, baurusuchids, and peirosaurids (Price, 1950, 1955, 1959; Gasparini, Chiappe & Fernandez, 1991; Carvalho & Bertini, 1999; Campos et al., 2001, 2011; Carvalho, Ribeiro & Avilla, 2004; Carvalho, Campos & Nobre, 2005; Andrade & Bertini, 2008; Kellner et al., 2009). Neosuchian material, by contrast, is much rarer, and most of the information about such fossils in the Brazilian basins of Cretaceous age is dubious, such as Goniopholis? paulistanus and ‘Hyposaurus derbianus’ (Cope, 1886; Roxo, 1936; Barbosa, Viana & Kellner, 2008). The presence of Sarcosuchus in Brazil is reliable, although as stated by Buffetaut & Taquet (1977) the possibility that S. hartii and S. imperator belong to the same species cannot be excluded.

The best Cretaceous neosuchian material from Brazil is from the Crato Formation Lagerstätte: Susisuchus anatoceps, and other related material (Salisbury et al., 2003; Frey & Salisbury, 2007; Figueiredo & Kellner, 2009). Further susisuchid material was recorded from the Lima-Campos Basin (Early Cretaceous) of north-east Brazil (Fortier & Schultz, 2009). Most fossils from the Araripe Basin unfortunately do not have precise locality data, hampering a more detailed understanding of the variations in faunal composition of this basin (Fara et al., 2005; Vila Nova et al., 2011). More structured and controlled excavations are necessary to define the relationships of these advanced neosuchians and the rest of the community of the Crato palaeoenvironment (Fara et al., 2005; Calvo et al., 2007; Vila Nova et al., 2011).

The new specimen (MPSC-R1136) shares with the Susisuchus anatoceps holotype (SMNK PAL 3804) at least three diagnostic features: (1) proximal and distal articulations of the ulna of about the same width but thicker than the relative thin shaft, which is also shared with Theriosuchus pusillus and Isisfordia duncani; (2) scapular blade with anterior straight margins and posterior concave margins; (3) ungual phalanges present only on digits 1 and 2 of the hand, although that is ambiguous due to the incompleteness of the digits in MPSC-R1136. The presence of two lateral rows of accessory osteoderms and amphicoelic thoracic vertebrae is also common for both taxa.

In MPSC-R1136 the dorsal shield comprises two paravertebral rows of sub-square osteoderms, in contrast to the four reported in Susisuchus anatoceps holotype (SMNK PAL 3804) and also different from Isisfordia duncani (Salisbury et al., 2003, 2006). This morphology is different from that of Bernissartia fagesii but similar to the as yet undescribed ‘Las Hoyas’ neosuchian (Buffetaut, 1975; Norell & Clark, 1990; Buscalioni, 1991; Ortega & Buscalioni, 1995; Salisbury & Frey, 2001). Benton & Clark (1988) consider the presence of more than two longitudinal rows of osteoderms as a derived character within the Neosuchia clade.

The sagittal segmentation of the paravertebral shield in forms with amphicoelic vertebrae is considered a transformational step in the transition to procoely (Norell & Clark, 1990; Buscalioni, 1991; Frey & Salisbury, 2007).The combination of these two characters is found in Bernissartia, the Las Hoyas neosuchian, and the holotype of Susisuchus (Buffetaut, 1975; Buscalioni, 1991; Clark & Norell, 1992; Salisbury et al., 2003).

The new specimen shows incipiently procoelous cervical vertebrae similar to the basal eusuchian Isisfordia duncani but differing from the holotype of Susisuchus anatoceps as described by Salisbury et al. (2003, 2006). The presence of procoelous vertebrae along with pterygoid-bounded choanae has traditionally been interpreted as a property of the Eusuchia (Huxley, 1875). Many fossil taxa, however, show some degree of procoely and lie outwith the eusuchian lineage and Clark (1994) suggests that this trait may have evolved independently multiple times in Crocodyliformes (see also Salisbury & Frey, 2001).

The degree of procoely normally decreases from the neck to tail (Salisbury & Frey, 2001; Rogers, 2003). MPSC-R1136 shows some procoelous cervical vertebrae, but the thoracic vertebrae are amphicoelous and hence are interpreted as an early stage of the transition to procoely. Salisbury et al. (2006) regard the incipient procoelous morphology of Isisfordia vertebrae as an intermediate condition between amphicoely and full procoely, and as it represents an adult individual of a ‘dwarf’ taxon, it is possible to exclude the ‘incipient morphology’ as a result of immaturity (Brochu, 1996; Salisbury et al., 2006). MPSC-R1136 does not represent a completely mature individual and therefore its vertebral bodies could have a more developed procoely.

Several features indicate that MPSC-R1136 represents a juvenile animal: lack of torsion on the humerus distal articulation and absence of conspicuous muscle scars on forelimb bones. Others are more suggestive of an adult: well-sculptured osteoderms, and partially closed sutures between neural arch and centrum of cervical and thoracic vertebrae. Some of these conditions are also found in the holotype of Susisuchus and corroborate the hypothesis that MPSC-R1136, as in the holotype, is not a completely mature individual (Salisbury et al., 2003).

The presence of well-developed hypapophyses on posterior cervical vertebrae is regarded as a synapomorphy of Eusuchia (Benton & Clark, 1988). The hypapophyses of MPSC-R1136 are small in comparison with those of extant taxa (Mook, 1921; Brochu, 1999), and they are also less developed than those from some atoposaurids (e.g. Theriosuchus spp.) and eusuchians, such as Stangerochampsa and Isisfordia (Wu, Brinkman & Russel, 1996; Salisbury, 2002; Schwarz & Salisbury, 2005; Salisbury et al., 2006). The neosuchian Gilchristosuchus palatinus has a keel-like hypapophysis similar to MPSC-R1136 (Wu & Brinkman, 1993), although this pattern is more common in basal Crocodylomorpha such as Shantungosuchus, Protosuchus, Sichuanosuchus, and Neuquensuchus (Colbert & Mook, 1951; Wu, Brinkman & Lu, 1994; Peng, 1996; Fiorelli & Calvo, 2007). Some notosuchian taxa (e.g. Notosuchus and Chimaerasuchus) also have hypapophyses in a ventral keel pattern (Wu & Sues, 1996; Pol, 2005).

Crocodylomorphan ribs have very conservative morphology and in general only those from the atlas and axis are considered to show phylogenetically informative characters (Mook, 1921; Benton & Clark, 1988; Brochu, 1997, 1999). Cervical ribs of MPSC-R1136 are interesting due to a narrowing between both the capitular and tubercular processes, which is typically a channel for ligaments and vessels of the neck (Reese, 1915); this feature is rare in crocodylomorphs.

The forelimb of MPSC-R1136 is quite derived, but the deltopectoral crest emerges smoothly from the proximal end of the humerus, differing from the extant crocodylomorphs (Mook, 1921); its proximal articulation is just slightly dorsoposteriorly deflected. The equivalent width of the proximal and distal extremities of the ulna is a trait shared by Susisuchus (both holotype and MPSC-R1136) with Theriosuchus and Isisfordia (Salisbury et al., 2006). The unusual presence of ungual phalanges only on digits 1 and 2 of the hand is regarded as diagnostic of Susisuchus anatoceps and is also present in MPSC-R1136.

MPSC-R1136 and Susisuchus anatoceps present a primitive scapular morphology with dorsal flare. The occurrence of subparallel edges without dorsal enlargement is accounted as a Crocodylia synapomorphy (Benton & Clark, 1988); however, it varies in some extant taxa such as Gavialis, Tomistoma, and Paleosuchus and also in fossil crocodylians, e.g. Wannaganosuchus and Stangerochampsa, in which the scapular blade flares dorsally (Erickson, 1982; Wu et al., 1996; Brochu, 1999). The presence of a scapula with straight anterior margin in combination with a concave posterior margin is only known in Susisuchus anatoceps.

Phylogenetic positioning

Susisuchus anatoceps was positioned as the sister group of Eusuchia by the original phylogenetic analysis of Salisbury et al. (2006), although later studies often failed to support this relationship (Delfino et al., 2008; Martin & Buffetaut, 2008; Jouve, 2009). To clarify the phylogenetic affinities of Susisuchus a reanalysis was carried out based on new information of the third specimen (MPSC-R1136) described herein.

We used the data matrix of Salisbury et al. (2006) with 176 characters (all unordered) and 43 ingroup taxa. Ten heuristic searches were completed, using Random Stepwise Addition in each one, with PAUP software (version 4.0b10; Swofford, 2003). There are five characters present in the new specimen of Susisuchus that were previously unknown in the holotype (see Appendix 1): (4–0) absence of diapophyses in the axis; (5–0) atlas intercentrum wedge-shaped; (8–1) weakly developed hypapophysis on first postaxial cervical vertebra; (25–1) broad scapulocoracoid facet cranial to glenoid fossa; (29–1) single scar from the insertion of teres major and dorsalis scapulae muscles. The coding of three other characters has changed from the original data set based on the new information present in MPSC-R1136: (9–0) neural spines on posterior cervical vertebrae as broad as those on anterior cervical vertebrae; (37–1) maximum of two longitudinal rows of transversely contiguous accessory osteoderms; (170–1) some cervical vertebrae amphicoelous and some procoelous.

Character 33 (proportion between forelimbs and hind limbs) was coded as 0 with both limbs approximately equal in length. The specimen regarded by Figueiredo & Kellner (2009) as cf. Susisuchus (MPSC-R1137), which comprises hind limb remains, is clearly a juvenile of a very small size even when compared with MPSC-R1136 and the holotype of Susisuchus anatoceps. Nevertheless, we regard limbs as being of similar size at maturity in this species.

Only one analysis of the original data set of Salisbury et al. (2006) was carried out, excluding Allodaposuchus precedens (sensuBuscalioni et al., 2001). Salisbury et al. (2006) cast doubts on the taxonomical validity of Allodaposuchus as described by Buscalioni et al. (2001); this was supported later by Delfino et al. (2008) who regarded it as a distinct taxon.

The analysis recovered 54 equally parsimonious trees [consistency index (CI): 0.4708; retention index (RI): 0.7668] with length of 480. The topology of the strict consensus fails to support the previous phylogenetic positioning of Susisuchus anatoceps, placing it in polytomy with the outgroup taxa (Theriosuchus and Goniopholis) and Bernissartia, Hylaeochampsa and Isisfordia (Fig. 9B).

image

Figure 9. Phylogenetic relationships of Susisuchus anatoceps. A, strict consensus of six most-parsimonious trees based on the data matrix of Jouve (2009). Each tree has 1374 steps and consistency index (CI) = 0.2991 and retention index (RI) = 0.6365. Only the Neosuchia clade is shown. B, strict consensus of 54 most-parsimonious trees based on the data matrix of Salisbury et al. (2006). Each tree has 480 steps and CI = 0.4708 and RI = 0.7668.

Download figure to PowerPoint

A second analysis was performed due the lack of resolution of the first. Susisuchus was recoded for the data set of Jouve (2009) using the new specimen data (see Appendix 2). Three characters were modified: (201–N) the scapular morphology of Susisuchus is unique, and this character was coded as ‘non-applicable’; (202–1) scapular blade very broad dorsally; (298–1) distal portion of humeral shaft flattened.

There are 13 other characters recorded for the first time for Susisuchus (MPSC-R1136 and MPSC-R1137): (203–1) scapula as long as coracoid; (206–0) olecranon well developed; (207–2) glenoid surface of coracoid extended obliquely; (214–1) proximal head of the radiale wider than distal head; (215–1) trochanteric fossa less than one-third of femur total length; (216–1) humeral shaft sigmoidal; (218–1) fifth pedal digit without phalanges; (219–0) atlas intercentrum broader than long; (220–0) neural spines on posterior cervical vertebrae as broad as those on anterior ones; (221–0) cervical vertebrae without well-developed hypapophysis; (222–1) cervical vertebrae semi-procoelous; (300–1) neural spine in axis located on posterior half; (328–0) length of humerus is more than two-thirds length of femur.

The same parameters of the first analysis were used in the second one. This new investigation recovered six most-parsimonious trees 1374 steps in length (CI: 0.2991, RI: 0.6365). The strict consensus topology shows three major clades of Neosuchia. The most basal of them is the Atoposauridae, which is composed of Theriosuchus pusillus + (Theriosuchus guimarotae + Montsecosuchus). A longirostrine clade appears as the sister group of the advanced neosuchians (Fig. 9A). The Thallatosuchia was not recovered as a part of Neosuchia.

Susisuchus is positioned as the most basal member of the advanced neosuchian clade. This result contradicts the previous hypothesis of Susisuchus as the sister taxon of Eusuchia but is consistent with some recent analyses (e.g. Pol et al., 2009), which also recovered an Asian clade formed by Rugosuchus and Shamosuchus as more closely related to Eusuchia than to Susisuchus. The positioning of Bernissartia as the sister taxon of Hylaeochampsa is not fully reliable, although these taxa are certainly close related to Eusuchia.

Final considerations

MPSC-R1136 is a small neosuchian showing a combination of both primitive crocodylomorphic traits and derived eusuchian characters. It is regarded here as a third specimen of Susisuchus anatoceps based on sharing at least three diagnostic features and coming from the same stratigraphic unit – perhaps even horizon – as the holotype, an important aspect for systematic purposes regarding fossils (e.g., Kellner 2010). MPSC-R1136 provides new anatomical information regarding the cervical vertebrae and dorsal armor morphology of Susisuchus anatoceps, both being poorly known on the holotype. Phylogenetic analysis confirms the position of this taxon as a basal member among advanced neosuchians.

ACKNOWLEDGEMENTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GEOLOGICAL SETTING
  5. SYSTEMATIC PALEONTOLOGY
  6. DESCRIPTION
  7. DISCUSSION
  8. ACKNOWLEDGEMENTS
  9. REFERENCES
  10. Appendices

We thank Hans Larsson (Redpath Museum/McGill University) and Steven Salisbury (University of Queensland) for critical comments that greatly improved the manuscript. Steven Salisbury and Stepháne Jouve (Muséum National d'Histoire Naturelle) are thanked for sending copies of their data matrices. We are also grateful to Gustavo Oliveira (Museu Nacional/UFRJ) for help with the photographs and André E. P. Pinheiro (Museu Nacional/UFRJ) for suggestions and discussion on the early versions of the manuscript. André E. P. Pinheiro made the drawing presented in Figure 2. This project was partially funded by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) (fellowship to R.G.F.) and Fundação Cearense de Apoio ao Desenvolvimento Científico e Tecnológico (FUNCAP) (fellowship to J.K.R.M.) with additional support by the Fundação Carlos Chagas de Amparo à Pesquisa do Rio de Janeiro (FAPERJ, grant number E-26/102.779/2008 to A.W.A.K.) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, grant numbers 501267/2008-5 and 307276/2009-0 to A.W.A.K.).

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GEOLOGICAL SETTING
  5. SYSTEMATIC PALEONTOLOGY
  6. DESCRIPTION
  7. DISCUSSION
  8. ACKNOWLEDGEMENTS
  9. REFERENCES
  10. Appendices
  • Andrade MB, Bertini RJ. 2008. A new Sphagesaurus (Mesoeucrocodylia: Notosuchia) from the Upper Cretaceous of Monte Alto City (Bauru Group, Brazil), and a revision of the Sphagesauridae. Historical Biology 20: 101136.
  • Assine ML. 1992. Análise Estratigráfica da Bacia do Araripe, Nordeste do Brasil. Revista Brasileira de Geociências 22: 289300.
  • Barbosa JA, Kellner AWA, Viana MSS. 2008. New dyrosaurid crocodylomorph and evidences for faunal turnover at the K–P transition in Brazil. Proceedings of the Royal Society B 275: 13851391.
  • Benton MJ, Clark JM. 1988. Archosaur phylogeny and the relationships of the Crocodylia. In: Benton MJ, ed. The phylogeny and classification of the tetrapods, volume 1: amphibians, reptiles, birds. Oxford: Oxford University Press, 295338.
  • Beurlen K. 1963. Geologia e estratigrafia da Chapada do Araripe. 17° Congresso Brasileiro de Geologia, Recife , 147.
  • Beurlen K. 1971. As condições ecológicas e faciológicas da Formação Santana na Chapada do Araripe (Nordeste do Brasil). Anais da Academia Brasileira de Ciências 43: 411415.
  • Brito-Neves BB. 1990. A Bacia do Araripe no contexto geotectônico regional. In: Campos DA, Viana MSS, Brito PM, Beurlen G, eds. Atas do simpósio sobre a Bacia do Araripe e Bacias Interiores do Nordeste. Crato: Departamento Nacional de Produção Mineral, 2133.
  • Brochu CA. 1996. Closure of neurocentral sutures during crocodilian ontogeny: implications for maturity assessment in fossil archosaurs. Journal of Vertebrate Paleontology 16: 4962.
  • Brochu CA. 1997. Morphology, fossils, divergence timing, and the phylogenetic relationships of gavialis. Systematic Biology 46: 479522.
  • Brochu CA. 1999. Phylogenetics, taxonomy, and historical biogeography of Alligatoroidea. Society of Vertebrate Paleontology Memoir 6: 9100.
  • Buffetaut E. 1975. Sur l'anatomie et la position systématique de Bernissartia fagesii Dollo, L., 1883, crocodilien Wealdien de Bernissart, Belgique. Bulletin de l'Institute Royal dês Sciences Naturelles de Belgique, Sciences de La Terre 51: 120.
  • Buffetaut E, Taquet P. 1977. The giant crocodilian Sarcosuchus in the Early Cretaceous of Brazil and Niger. Paleontology 20: 203208.
  • Buscalioni AD. 1991. Historia evolutiva de los Crocodylomorpha. In: Sanz JL, Buscalioni AD, eds. Los Dinosaurios y su Entorno Biotico. Cuenca: Instituto Juan de Valdés, 307344.
  • Buscalioni AD, Ortega F, Weishampel DB, Jianu CM. 2001. A revision of the Crocodyliform Allodaposuchus precedens from the Upper Cretaceous of the Hateg Basin, Romania. Its relevance in the phylogeny of Eusuchia. Journal of Vertebrate Paleontology 21: 7486.
  • Calvo JO, Porfiri JD, González-Riga J, Kellner AWA. 2007. A new Cretaceous terrestrial ecosystem from Gondwana with the description of a new sauropod dinosaur. Anais da Academia Brasileira de Ciências 79: 529541.
  • Campos DA, Oliveira GR, Figueiredo RG, Riff D, Azevedo SAK, Carvalho LB, Kellner AWA. 2011. On a new peirosaurid crocodyliform from the Upper Cretaceous, Bauru Group, southeastern Brazil. Anais da AcademiaBrasileira de Ciências 83: 317327.
  • Campos DA, Suarez JM, Riff D, Kellner AWA. 2001. Short note on a new Baurusuchidae (Crocodyliformes, Metasuchia) from the Upper Cretaceous of Brazil. Boletim do Museu Nacional, Nova Série Geologia 57: 18.
  • Carvalho IS, Bertini RJ. 1999. Mariliasuchus: um novo Crocodylomorpha (Notosuchia) de Cretáceo da Bacia Bauru, Brasil. Geología Colombiana 24: 83105.
  • Carvalho IS, Ribeiro LCB, Avilla LS. 2004. Uberabasuchus terrificus sp. nov., a New Crocodylomorpha from the Bauru Basin (Upper Cretaceous), Brazil. Gondwana Research 7: 9751002.
  • Carvalho IS, Campos ACA, Nobre PH. 2005. Baurusuchus salgadoensis, a new Crocodylomorpha from the Bauru Basin (Cretaceous), Brazil. Gondwana Research 8: 1130.
  • Clark JM. 1994. Patterns of evolution in Mesozoic Crocodyliformes. In: Fraser NC, Sues HD, eds. In the shadow of the dinosaurs. Cambridge: Cambridge University Press, 8497.
  • Colbert EH, Mook CC. 1951. The ancestral crocodilian Protosuchus. Bulletin of the American Museum of Natural History 97: 143182.
  • Cope ED. 1886. A contribution to the vertebrate paleontology of Brazil. Proceedings of the American Philosophical Society 23: 120.
  • Delfino M, Codrea V, Folie A, Dica P, Godefroit P, Smith T. 2008. A complete skull of Allodaposuchus precedens Nopcsa, 1928 (Eusuchia) and a reassessment of the morphology of the taxon based on the Romanian remains. Journal of Vertebrate Paleontology 28: 111122.
  • Erickson BR. 1982. Wannaganosuchus, a new alligator from the Paleocene of North America. Journal of Paleontology 56: 492506.
  • Fara E, Saraiva AÁF, Campos DA, Moreira JKR, Siebra DC, Kellner AWA. 2005. Controlled excavations in the Romualdo Member of the Santana Formation (Early Cretaceous, Araripe basin, northeastern Brazil): stratigraphic, palaeoenvironmental and palaeoecological implications. Palaeogeography, Palaeoclimatology, Palaeoecology 218: 145160.
  • Figueiredo RG, Kellner AWA. 2009. A new crocodylomorph specimen from the Araripe Basin (Crato Member, Santana Formation) northeastern Brazil. Paläontologische Zeitschrift 83: 323331.
  • Fiorelli LE, Calvo JO. 2007. The first ‘Protosuchian’ (Archosauria: Crocodyliformes) from the Cretaceous (Santonian) of Gondwana. Arquivos do Museu Nacional 65: 417459.
  • Fortier DC, Schultz CL. 2009. A new neosuchian Crocodylomorph (Crocodyliformes, Mesoeucrocodylia) from the Early Cretaceous of North-East Brazil. Palaeontology 52: 9911007.
  • Frey E, Salisbury SW. 2007. Crocodilians of the Crato Formation: evidence for enigmatic species. In: Martill DM, Bechly G, Loveridge RF, eds. The Crato fossil beds of Brazil: window into an ancient world. New York: Cambridge University Press, 463476.
  • Gasparini Z, Chiappe LM, Fernandez M. 1991. A new senonian peirosaurid (Crocodylomorpha) from Argentina and a synopsis of the South American Cretaceous crocodilians. Journal of Vertebrate Paleontology 11: 316333.
  • Hecht MK. 1991. Araripesuchus P 1959. In: Maisey JG, ed. Santana fossils: an ilustrated atlas. Neptune City: T.F.H. Publications, 342347.
  • Huxley TH. 1875. On Stagonolepis robertsoni, and on the evolution of the Crocodilia. Quarterly Journal of the Geological Society 31: 423438.
  • Jouve S. 2009. The skull of Teleosaurus cadomensis (Crocodylomorpha; Thalattosuchia), and phylogenetic analysis of Thalattosuchia. Journal of Vertebrate Paleontology 29: 88102.
  • Kellner AWA. 1987. Ocorrência de um Novo Crocodiliano no Cretáceo Inferior da Bacia do Araripe, Nordeste do Brasil. Anais da Academia Brasileira de Ciências 59: 219232.
  • Kellner AWA. 1994. Comments on the paleobiogeography of Cretaceous archosaurs during the opening of the South Atlantic Ocean. Acta Geologica Leopoldensia 39: 615625.
  • Kellner AWA. 2010. Comments on the Pteranontidae (Pterosauria, Pterodactyloidea) with the description of two new species. Anais da Academia Brasileira de Ciências 82: 10631084.
  • Kellner AWA, Campos DA. 1999. Vertebrate paleontology in Brazil – a review. Episodes 22: 238251.
  • Kellner AWA, Maisey JG, Campos DA. 1994. Fossil down feather from the Lower Cretaceous of Brazil. Paleontology 37: 489492.
  • Kellner AWA, Pinheiro AEP, Azevedo SAK, Henriques DDR, Carvalho LB, Oliveira GR. 2009. A new crocodyliform from the Alcântara Formation (Cenomanian), Cajual Island, Brazil. Zootaxa 2030: 4958.
  • Maisey JG, ed. 1991. Santana fossils: an illustrated atlas. Neptune City: T.F.H. Publications.
  • Martin JE, Buffetaut E. 2008. Crocodilus affuvelensis Matheron, 1869 from the Late Cretaceous of southern France: a reassessment. Zoological Journal of the Linnean Society 152: 567580.
  • Meers MB. 2003. Crocodylian forelimb musculature and its relevance to Archosauria. The Anatomical Record Part A 274: 891916.
  • Mook CC. 1921. Notes on the postcranial skeleton in the Crocodilia. Bulletin of the American Museum of Natural History 44: 67100.
  • Neumann VH, Cabrera L. 1999. Una nueva propuesta estratigráfica para La tecnosecuencia post-rifte de la cuenca de Araripe, Noreste de Brasil. 5° Simpósio sobre o Cretáceo do Brasil, Serra Negra , 279285.
  • Neumann VH, Cabrera L. 2002. Características hidrogeológicas gerais, mudanças de salinidade e caráter endorréico do sistema lacustre cretáceo do Araripe, NE Brasil. Revista de Geologia 15: 4354.
  • Norell MA, Clark JM. 1990. A reanalysis of Bernissartia fagesii, with comments on its phylogenetic position and its bearing on the origin and diagnosis of the Eusuchia. Bulletin de l'Institute Royal des Sciences Naturelles de Belgique, Sciences de La Terre 60: 115128.
  • Ortega F, Buscalioni AD. 1995. Las Hoyas crocodiles, an evidence of the transition model of the eusuchian dorsal armour configuration. II International Symposium on Lithographic Limestones, Lleida-Cuenca , 5356.
  • Peng GZ. 1996. [A Late Jurassic protosuchian Sichuanosuchus huidongensis from Zigong, Sichuan Province]. Vertebrata PalAsiatica 34: 269278 [in Chinese].
  • Pol D. 2005. Postcranial remains of Notosuchus terrestris (Archosauria: Crocodyliformes) from the Upper Cretaceous of Patagonia, Argentina. Ameghiniana 42: 2138.
  • Pol D, Turner AT, Norell MA. 2009. Morphology of the Late Cretaceous crocodylomorph Shamasuchus djadochtaensis and a discussion of Neosuchian phylogeny as related to the origin of Eusuchia. Bulletin of the American Museum of Natural History 324: 1103.
  • Pons D, Berthou PY, Campos DA. 1990. Quelques observations sur la palynologie de l'Aptien supérieur et del'Albien do bassin d'Araripe (N-E du Brasil). In: Campos DA, Viana MSS, Brito PM, Beurlen G, eds. Atas do Simpósio sobre a Bacia do Araripe e Bacias interiores do Nordeste. Crato: Departamento Nacional de Produção Mineral, 142252.
  • Ponte FC, Ponte Filho FC. 1996. Evolução tectônica e classificação da Bacia do Araripe. 4° Simpósio sobre o Cretáceo do Brasil, Águas de São Pedro-Rio Claro , 123133.
  • Price LI. 1950. On a new crocodilian, Sphagesaurus, from the Cretaceous of the State of São Paulo, Brazil. Anais da Academia Brasileira de Ciências 22: 7785.
  • Price LI. 1955. Novos Crocodilídeos dos arenitos da Série Baurú, Cretáceo do Estado de Minas Gerais. Anais da Academia Brasileira de Ciências 27: 487498.
  • Price LI. 1959. Sobre um Crocodilídeo Notossúquio do Cretáceo Brasileiro. Boletim do Departamento Nacional de Produção Mineral/Divisão de Geologia e Mineralogia 188: 155.
  • Reese AM. 1915. The alligator and its allies. New York: The Knickerbocker Press.
  • Rogers JVI. 2003. Pachycheilosuchus trinquei, a new procoelous crocodyliform from the Lower Cretaceous (Albian) Glen Rose Formation of Texas. Journal of Vertebrate Paleontology 23: 128145.
  • Roxo MO. 1936. On a new species of fossil Crocodilia from Brazil, Goniopholis paulistanus sp. n. Anais da Academia Brasileira de Ciências 8: 3334.
  • Salisbury SW. 2002. Crocodilians from the Lower Cretaceous (Berriasian) Purbeck Limestone Group of Dorset, southern England. Special Papers in Palaeontology 68: 121144.
  • Salisbury SW, Frey E. 2001. A biomechanical transformation model for the evolution of semi-spheroidal articulations between adjoining vertebral bodies in crocodilians. In: Grigg GC, Seebacher F, Franklin CE, eds. Crocodilian biology and evolution. Chipping Norton: Surrey Beatty & Sons, 85134.
  • Salisbury SW, Frey E, Martill DM, Buchy MC. 2003. A new crocodilian from the Lower Cretaceous Crato Formation of north-eastern Brazil. Paleontographica Abteilung A 270: 347.
  • Salisbury SW, Molnar RE, Frey E, Willis PMA. 2006. The origin of modern crocodyliforms: new evidence from the Cretaceous of Australia. Proceedings of The Royal Society B 273: 24392448.
  • Schwarz D, Salisbury SW. 2005. A new species of Theriosuchus (Atoposauridae, Crocodylomorpha) from the Late Jurassic (Kimmeridgian) of Guimarota, Portugal. Geobios 38: 779802.
  • Swofford DL. 2003. PAUP*: phylogenetic analysis using parsimony (*and other methods). Version 4. Sunderland, MA: Sinauer Associates.
  • Vila Nova BC, Saraiva AAF, Moreira JKR, Sayão JM. 2011. Controlled excavations in the Romualdo Formation Lagerstätte (Araripe Basin, Brazil) and pterosaur diversity: remarks based on new findings. PALAIOS 26: 173179.
  • Walker AD. 1970. A revision of the Jurassic reptile Hallopus victor (Marsh), with remarks on the classifications of the crocodiles. Philosophical Transactions of the Royal Society of London Series B 257: 323372.
  • Whetstone KN, Whybrow PJ. 1983. A ‘cursorial’ crocodilian from the Triassic of Lesotho (Basutoland), southern Africa. Occasional Papers of the Museum of Natural History of the University of Kansas 106: 137.
  • Wu XC, Brinkman DB. 1993. A new crocodylomorph of ‘mesosuchian’ grade from the Upper Cretaceous upper Milk River Formation, southern Alberta. Journal of Vertebrate Paleontology 13: 153160.
  • Wu XC, Sues HD. 1996. Anatomy and phylogenetic relationships of Chimaerasuchus paradoxus, an unusual crocodyliform reptile from the Lower Cretaceous of Hubei, China. Journal of Vertebrate Paleontology 16: 688702.
  • Wu XC, Brinkman DB, Lu JC. 1994. A new species of Shantungosuchus from the Lower Cretaceous of Inner Mongolia (China), with comments on S. chuhsienensis Young, 1961 and the phylogenetic position of the genus. Journal of Vertebrate Paleontology 14: 210229.
  • Wu XC, Brinkman DB, Russel AP. 1996. A new alligator from the Upper Cretaceous of Canada and the relationships of Early Eusuchians. Palaeontology 39: 351375.

Appendices

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. GEOLOGICAL SETTING
  5. SYSTEMATIC PALEONTOLOGY
  6. DESCRIPTION
  7. DISCUSSION
  8. ACKNOWLEDGEMENTS
  9. REFERENCES
  10. Appendices

APPENDIX 1

New character coding (176 characters) of Susisuchus anatoceps based on MPSC-R1136 and following the data set of Salisbury et al. (2006).

???00 NN10? ??01? ??0N0 N0001 00?1? ??0?0 22310 ????? ????1 1???? ????1 ????? ???10 ????0 11010 02?0? 00?3? ?12?2 ?0??0 0?000 0???? 00??? ?0??0 0?1?? ????? 2??00 ???00 10000 0???0 ????? ????? 0???0 ???11 0?001 1

APPENDIX 2

New character coding (343 characters) of Susisuchus anatoceps based on MPSC-R1136 and following the data set of Jouve (2009).

20013 00113 00100 1???? ???01 ?01?0 010?0 ??0?0 ?0001 2011? 11??? ?0010 11000 ????1 0110? 000?? ?0010 10010 011?1 011?1 0?0?? ???01 ????? ????? ????? ????1 1???? ??0?? ??1?? ????? ????? ????? ????? ????? ???00 11??? 00100 00?01 00000 00??1 N11?? 02??? ?0111 1?100 01000 20101 0010? 1000? 1???? ?0??? ?1000 000?0 0??00 00010 00?0? ????? 0?0?? ???0? ????? 001?1 ?0000 00011 00??0 0?000 ??0?? 0?001 ?1?0? ?100? 00?

APPENDIX 3

Measurements of the appendicular skeleton ofSusisuchus anatoceps (MPSC-R1136)

All measures are given in mm.

inline image