Araripesuchus wegeneri Buffetaut &amp; Taquet 1979
Creators: name: Sereno, Paul
name: Larsson, Hans
Publisher: name: Zenodo
Year: 2009
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Reptilia
Crocodylia
Araripesuchus
Araripesuchus wegeneri

description: <i>Araripesuchus wegeneri</i> Buffetaut &amp; Taquet, 1979 Figs. 14–26 Tables 6–8 Buffetaut and Taquet (1979, fig. 1) Ortega et al. (2000, fig. 9) Turner (2006, figs. 5–7) <b>Holotype.</b> MNHN GDF700; snout composed of articulated upper and lower jaws and preserved to mid-orbit on the right side with several teeth preserving their crowns. <b>Type locality.</b> Gadoufaoua, Agadez District, Niger Republic (more precise locality unknown) (Fig. 1A, C). <b>Horizon.</b> Elrhaz Formation, Tegama Series; Lower Cretaceous (Aptian-Albian), ca. 110 Mya (Taquet 1976). <b>Referred material.</b> MNN GAD 19, nearly complete cranium lacking only portions of the left lacrimal and prefrontal, the palpebrals, and some of the teeth (Figs. 14–17, 19); MNN GAD 20, partial skeleton on block preserving the left side of the skull exposing the dentition in medial view and an articulated tail with dermal armor (Figs. 20, 21, 25A); MNN GAD 21, partial skeleton on block preserving the ventral portion of the skull, an articulated partial forelimb, and an articulated tail with dermal armor (Fig. 24, 25B); MNN GAD 22, partial skeleton on block preserving the ventral portion of the skull, an articulated right manus and pes, a right calcaneum, and an articulated tail with dermal armor (Fig. 26); MNN GAD 23, isolated snout on block composed of articulated upper and lower jaws and preserved to mid-orbit on the right side; MNN GAD 24, isolated left maxilla on block preserving the dentition; MNN GAD 25, partial skeleton preserving the posterior ends of the lower jaws and most of the postcranial skeleton except the tail; MNN GAD 26, edentulous right dentary from a juvenile (Fig. 18). An exceptional series of specimens are preserved in close proximity on a single block of sandstone (MNN GAD 20–24) (Fig. 23). Th ree individuals are fairly complete, partially articulated skeletons with their axial columns aligned side-by-side pointing in the same direction (MNN GAD 20–22). One of the three (MNN GAD 20) is slightly small- er than the other two. Also present are portions of at least two additional individuals, one represented by an articulated snout (MNN GAD 23) and the other by an isolated maxilla (MNN GAD 24). A minimum of five individuals thus are represented on the block. The close proximity and alignment of the three best preserved skeletons and the presence of additional individuals on a small block is unusual. Portions of the three best preserved skeletons (MNN GAD 20–22) and the isolated snout (MNN GAD 23) have been lost to postmortem surface erosion and would have been more complete. Some postmortem disarticulation is evident in all three of the most complete specimens (MNN GAD 20–22), although there is no obvious preferred direction or orientation to displaced elements. Th e strong curvature of the distal tail in three skeletons, in addition, is diffi cult to attribute to postmortem water transport, as the curvature in one of the skeletons opposes the curvature in the other two. <b>Revised diagnosis.</b> Small-bodied metasuchian (&lt;1.0 m) characterized by an anterior premaxillary foramen anterior to the first premaxillary tooth; infratemporal bar of jugal with marginal fossa; supratemporal fossa with marked anteromedial corner; scalloped posterior margin of skull table with median process; reduction of the premaxillary palate to parasagittal shelves; median elliptical incisive foramen; dentary with prominent labial alveolar margin that obscures all alveoli in lateral view; caniniform (d4) to the largest crowns in the postcaniniform series (d13) with relatively low, mesiodistally broad (crown width 60–80% of crown height), denticulate crowns; and largest postcaniniform crowns with lingually deflected mesial carina and associated trough. <b>Discussion.</b> The referred cranium (MNN GAD19; Figs. 14–17, 19) removes any doubt about the assignment of the African species to <i>Araripesuchus</i>; the shape of the cranium and many of its structural details are close or identical with the type species <i>Araripesuchus gomesii</i> (Price 1959). <b> Figure |4. Skull of the crocodyliform <i>Araripesuchus wegeneri</i>.</b> Cranium (MNN GAD19). <b>A</b> Lateral view (reversed). <b>B</b> Dorsal view. <b>C</b> Ventral view. Scale bar equals 5 cm. Secondly, there is no doubt that cranium MNN GAD19 is correctly referred to <i>A. wegeneri</i>, because there are many features it shares only with the holotype, a partial snout (MNHN GDF700; Buffetaut and Taquet 1979). It is approximately 90% of the size of the holotype, based on measurements of the snout. Both have five premaxillary teeth. Th e jugal in both specimens expands in depth toward its anterior end and has a shallow sculpted fossa under the orbit. Other shared features found thus far only in the holotype and MNN GAD19 include a premaxillary sinus, small posterior spine on the maxilla that projects into the antorbital fenestra, flat strap-shaped border between the <b> Figure |5. Skull of the crocodyliform <i>Araripesuchus wegeneri</i>.</b> Drawings matching the cranium (MNN GAD19) in Fig. 14. <b>A</b> Lateral view (reversed). <b>B</b> Dorsal view. <b>C</b> Ventral view. Parallel lines indicate broken bone surface; dashed line indicates missing bone or tooth crown; grey tone indicates matrix. Scale bar equals 5 cm. Abbreviations: <i>am3</i>, <i>14</i>, alveolus for maxillary tooth 3, 14; <i>antfe</i>, antorbital fenestra; <i>antfo</i>, antorbital fossa; <i>apap</i>, articular surface for palpebral; <i>apm1</i>, alveolus for premaxillary tooth 1; <i>apmf</i>, anterior premaxillary foramen; <i>aqj</i>, articular surface for the quadratojugal; <i>be</i>, buccal emargination; <i>bo</i>, basioccipital; <i>bs</i>, basisphenoid; <i>bt</i>, basal tubera; <i>ch</i>, choana; <i>cqp</i>, cranioquadrate passage; <i>ec</i>, ectopterygoid; <i>Ef</i>, Eustachian foramen; <i>en</i>, external naris; <i>f</i>, frontal; <i>fl</i>, flange; <i>fo</i>, foramen; <i>gef</i>, groove for ear flap; <i>j</i>, jugal; <i>l</i>, lacrimal; <i>lf</i>, lacrimal foramen; <i>ls</i>, laterosphenoid; <i>m</i>, maxilla; <i>m1, 3</i>, <i>7</i>, maxillary tooth 1, 3, 7; <i>n</i>, nasal; <i>nfo</i>, narial fossa; <i>oc</i>, occipital condyle; <i>ot</i>, otoccipital; <i>p</i>, parietal; <i>pf</i>, prefrontal; <i>pl</i>, palatine; <i>pm</i>, premaxilla; <i>pm3, 5</i>, premaxillary tooth 3, 5; <i>pmmf</i>, premaxilla-maxilla foramen; <i>po</i>, postorbital; <i>popr</i>, paroccipital process; <i>pos</i>, preotic siphonium; <i>pt</i>, pterygoid; <i>q</i>, quadrate; <i>qj</i>, quadratojugal; <i>se</i>, septum; <i>sq</i>, squamosal; <i>so</i>, supraoccipital; <i>sof</i>, suborbital fenestra. choana and suborbital fenestra, and a V-shaped anterior margin of the choanae (Figs. 14, 15, 17). Finally, the fifth maxillary crown is preserved in both skulls and corresponds in detail regarding orientation, shape, and surface detail; the subcircular crown is angled posteroventrally, has a low short primary ridge near the crown apex laterally, has finely denticulate carinae, and has fine striations on the crown surface, some of which extend from the denticles. <b>Dorsal skull roof.</b> The following abbreviate description is based primarily on the well preserved cranium MNN GAD19 (Figs. 14–17, 19, 22; Table 7) and a nearly complete dentition in skull MNN GAD20, which was hemisected by erosion (Figs. 20, 21). The <i>premaxilla</i> exhibits many features important for determining phylogenetic position, the monophyly of <i>Araripesuchus</i>, and the distinction of <i>A. wegeneri</i>. Most of the external surface of the bone is smooth, except for the tip of the posterodorsal ramus (Figs. 14A, B, 15A, B, 16A). At the anterior tip of the premaxilla, an anterior premaxillary foramen is present and passes posterodorsally into the nasal passage (Fig. 16A). On the lateral aspect of the premaxilla, the posterior boundary of the narial fossa is indicated by an arcuate depression, posterior to which are located two large neurovascular foramina (posterior premaxillary foramina) and one smaller accessory foramen. One large foramen with a similar anteroventral groove has been described or shown in <i>A. gomesii</i> (Price 1959) (also AMNH 24450), <i>A. patagonicus</i> (Ortega et al. 2000) and <i>A. tsangatsangana</i> (Turner 2006). Posterior to these foramina is located the larger premaxillamaxilla foramen, which opens between these bones and extends ventrally to the alveolar margin as a narrow slit (Fig. 16A). In cross-section the body of the premaxilla posterior to the external nares is hollow (Fig. 17A), a highly unusual feature that is at least partially responsible for the inflated appearance of the premaxilla (Fig. 16A). Th is space, a premaxillary sinus, is also visible on the holotype, the cavity filled with matrix and exposed by erosion (MNHN GDF700). In the scan of <i>A. wegeneri</i> and in an acid-prepared skull of <i>A. gomesii</i> (AMNH 24450; Hecht 1991), the canal of the premaxilla-maxilla foramen appears to have an anterior diverticulum that may pneumatize the premaxilla. The scan also shows that the pair of large lateral foramina on the body of the premaxilla anterior to the premaxilla-maxilla foramen also communicate with the premaxillary sinus. The external surface of the <i>maxilla</i> is textured, except for a smooth surface along the arched, ventral alveolar margin dorsal to the postcaniniform teeth (Figs. 14A, 15A, 16A). Th e root of the caniniform tooth fills the swelling at the anterior end of the maxilla. Th e maxilla extends posteriorly to form the anterior margin of the antorbital fenestra and fossa. Above the fossa, a narrow prong of the maxilla contacts the prefrontal, separating the nasal and lacrimal. Th is is a sutural configuration present in <i>A. tsangatsangana</i> but absent in <i>A. gomesii</i> and <i>A. patagonicus</i> (Turner 2006), where the nasal contacts the lacrimal separating the maxilla and prefrontal. The <i>nasal</i> is textured most deeply with circular pits in its mid-section and has a more elevated median nasal bridge than in other species (Figs. 14B, 15B). The nasalfrontal suture is interdigitated as in <i>A. gomesii</i> (Price 1959) and <i>A. patagonicus</i> (Ortega et al. 2000), a sutural configuration present in juveniles of <i>A. gomesii</i> (AMNH 24450). structures measured on left side except as indicated. 1 Measurement from right side. The nasal-frontal suture shows less interdigitation in <i>A. tsangatsangana</i> (Turner 2006), and the frontal has a narrow anteromedian process in <i>A. buitreraensis</i> (Pol and Apesteguia 2005). The L-shaped <i>lacrimal</i> forms nearly all of the smooth surface of the antorbital fossa, which has subequal margins posterior and ventral to the antorbital fenestra as in <i>A. gomesii</i> (Figs. 14A, 15A). Th e narrow continuation of the smooth margin of the fossa extends around the anterior corner of the antorbital fenestra and along the ventral margin of a posterior prong of the maxilla that partially divides the fenestra. None of the other species of <i>Araripesuchus</i> have a similar maxillary prong. In both <i>A. gomesii</i> and <i>A. patagonicus</i> (Ortega et al. 2000), the antorbital fossa is approximately twice the size of the opening in <i>A. wegeneri</i> relative to the orbit and does not appear to change much in rela- <b> Figure |6. Skull of the crocodyliform <i>Araripesuchus wegeneri</i>.</b> Detailed views of the cranium (MNN GAD19). <b>A</b> Snout margin in anterolateral view. <b>B</b> Posterior portion of the skull in left lateral view. <b>C</b> Posterior palate in ventral view. Scale bars equal 2 cm. Abbreviations: <i>apap</i>, articular surface for the palpebral; <i>apmf</i>, anterior premaxillary foramen; <i>be</i>, buccal emargination; <i>cqp</i>, cranioquadrate passage; <i>ch</i>, choana; <i>ec</i>, ectopterygoid; <i>fo</i>, foramen; <i>fov</i>, fenestra ovalis; <i>gef</i>, groove for the ear flange; <i>j</i>, jugal; <i>pm,</i> premaxilla; <i>qj</i>, quadratojugal; <i>m</i>, maxilla; <i>m3</i>, maxillary tooth 3; <i>mco</i>, medial condyle; <i>n</i>, nasal; <i>nf</i>, narial fossa; <i>p</i>, parietal; <i>pl</i>, palatine; <i>pm</i>, premaxilla; <i>pm3, 5</i>, premaxillary tooth 3, 5; <i>pmmf</i>, premaxilla-maxilla foramen; <i>po</i>, postorbital; <i>pos</i>, preotic siphonium; <i>ppmf</i>, posterior premaxillary foramen; <i>pt</i>, pterygoid; <i>ptfl</i>, pterygoid flange; <i>q</i>, quadrate; <i>se</i>, septum; <i>sof,</i> suborbital fenestra; <i>sq</i>, squamosal. <b> Figure |7. Skull of the crocodyliform <i>Araripesuchus wegeneri</i>.</b> Computed-tomographic cutaway views of the cranium (MNN GAD19). <b>A</b> Snout posterior to the external nares in anterior view. <b>B</b> Posterior portion of the skull in anterior view. <b>C</b> Cranium in sagittal section near midline. Scale bar for A and B equals 2 cm; scale bar for C equals 3 cm. Abbreviations: <i>ch</i>, choana; <i>cr</i>, crest; <i>ec</i>, ectopterygoid; <i>Euc</i>, Eustachian canal; <i>f,</i> frontal; <i>fm</i>, foramen magnum; <i>j</i>, jugal; <i>lu,</i> lumen; <i>m</i>, maxilla; <i>m3, 7</i>, maxillary tooth 3, 7; <i>n</i>, nasal; <i>np</i>, narial passage; <i>pl</i>, palatine; <i>pm</i>, premaxilla; <i>pm3, 5</i>, premaxillary tooth 3, 5; <i>po</i>, postorbital; <i>popr</i>, paroccipital process; <i>prf</i>, prefrontal; <i>pt</i>, pterygoid; <i>ptfl</i>, pterygoid flange; <i>q</i>, quadrate; <i>se</i>, septum; <i>sq</i>, squamosal; <i>v</i>, vomer. tive size after reaching subadult size in <i>A. gomesii</i> (Price 1959; Hecht 1991). The opening is proportionately largest in <i>A. tsangatsangana</i> and appears to lack any smooth surface attributable to an antorbital fossa (Turner 2006). A prominent knob and ridge are situated on the lacrimal dorsal to the fossa and are continuous posteriorly with the edge of a large anterior palpebral. Th e lacrimal foramen is located ventral to this knob within the orbit. The anterior and posterior <i>palpebrals</i> are missing in cranium MNN GAD19, exposing articular fossae on the lacrimal and <i>prefrontal</i> anteriorly and on the postorbital posteriorly (Figs. 14B, 15B). Disarticulated palpebrals have been discovered on the large block (Fig. 23). In <i>A. wegeneri</i> the interdigitating prefrontal-frontal suture contrasts with the broad scarf joint described in <i>A. tsangatsangana</i> (Turner 2006). The prefrontal pillar is anteroposteriorly flattened and angles ventromedially and slightly posteriorly, tapering strongly from the skull roof to the palate. The <i>frontal</i> and <i>parietal</i> are fused to their opposites and join each other by an interdigitating frontoparietal suture. Th e frontals have a distinct median crest, and the parietal skull table between the supratemporal fossae is noticeably narrower than in other species of <i>Araripesuchus</i>. In <i>A. wegeneri</i> a parasagittal line extending along the orbital margin passes across the supratemporal fossa rather than along its lateral rim as in other species (Figs. 14B, 15B). Th e frontal enters the supratemporal fossa to a greater degree than in other species of <i>Araripesuchus</i>, reaching the inner margin of the fossa in dorsal view. The rim of the fossa in <i>A. wegeneri</i> also has a marked anteromedial corner with parasagittal and transverse edges, whereas in other species the rim of the fossa is nearly uniformly curved. Th e posterior margin of the skull table in <i>A. wegeneri</i> is scalloped to each side of the supraoccipital, differing from the nearly straight posterior margin in other species. The <i>postorbital</i> is notched by an articular facet for a small posterior palpebral, as in other species of <i>Araripesuchus</i> and most stem crocodyliforms. Th e surface of the postorbital between this facet and the supratemporal fossa varies, remaining textured with pits in some species, such as <i>A. gomesii</i> (Price 1959) and <i>A. tsangatsangana</i> (Turner 2006), and smooth in others such as <i>A. patagonicus</i> (Ortega et al. 2000). In <i>A. wegeneri</i> this surface is smooth and convex (Figs. 14B, 15B) rather than flat with a sharp medial and lateral rims as in many protosuchians and neosuchians. The <i>squamosal</i> is distinctly triradiate in dorsal view in <i>A. wegeneri</i> and all other species except <i>A. gomesii</i>. The difference lies in the length and orientation of the posterior process, which has more subdued pitting and is offset below the skull table. The posterior process appears to be both shorter and angled more steeply posteroventrally in <i>A. gomesii</i>, such that it appears to be of negligible length in dorsal view of the skull (Price 1959; Hecht 1991). Th e pitted dorsal surface of the squamosal in <i>A. wegeneri</i> has an L-shaped fossa where the pitted texture is depressed, a condition more strongly expressed in <i>Simosuchus</i> (Buckley et al. 2000). The anterior ramus of the <i>jugal</i> extends as a broad process as far anteriorly as the lacrimal, approaching the border of the antorbital fossa with a narrow fingerlike process. The anterior ramus is not as deep or extended anteriorly in either <i>A. patagonicus</i> (Ortega et al. 2000) or <i>A. tsangatsangana</i> (Turner 2006). The base of the smooth rod-shaped dorsal ramus, which is inset from the textured body of the jugal and pierced by a si- phonal foramen, is situated on the posterior one-half of the jugal (Figs. 14A, 15A). The posterior ramus of the jugal is distinctive. As in <i>A. gomesii</i> but unlike other species, the ramus tapers to a point below the posterior corner of the laterotemporal fenestra rather than at mid-length along the infratemporal bar. Unique to <i>A. wegeneri</i>, a marginal fossa with reduced texture is present along the dorsal margin of the posterior ramus. 1 Right side. The L-shaped <i>quadratojugal</i> has an inset articular facet for the posterior ramus of the jugal. Th e quadratojugal-quadrate contact adjacent to the condyles and along the shaft is an interdigitating suture. Texturing of the external surface of the quadratojugal is limited to the posteroventral corner, where the bone approaches, but does not contribute to, the articular surface for the lower jaw. <b>Palate.</b> The configuration of the anterior palate in <i>A. wegeneri</i> is unusual compared to that in <i>A. gomesii</i> (Price 1959) and other basal metasuchians. The premaxillary contribution is limited to the periphery of the anterior palate adjacent to the alveolar margin. Opposing premaxillae have very little contact on the palate. Th ey join in the midline only anterior and posterior to an elliptical incisive foramen (Figs. 14C, 15C). Most of the palate between the premaxillary tooth rows is formed by the maxillae. A pit for reception of the tip of the dentary caniniform is present at the premaxilla-maxilla suture medial to the premaxilla-maxilla foramen. Th e tip of the dentary caniniform in this location can be seen in the articulated dentition of MNN GAD20 (Fig. 20B). The configuration of the remainder of the palate, including the <i>palatine</i>, <i>ectopterygoid</i> and <i>pterygoid</i>, is quite similar to that in <i>A. gomesii</i> (Price 1959) and <i>A. tsangatsangana</i> (Turner 2006). Th e semicircular suborbital fenestra is larger than the adjacent choana, which is situated farther posteriorly on the palate, although not butted against the posterior transverse edge of the pterygoids (Figs. 14C, 15C). <i>A. patagonicus</i> is unusual in this regard, with the posterior ma
description: Published as part of <i>Sereno, Paul &amp; Larsson, Hans, 2009, Cretaceous Crocodyliforms from the Sahara, pp. 1-143 in ZooKeys 28 (28)</i> on pages 34-55, DOI: 10.3897/zookeys.28.325, http://zenodo.org/record/576570
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