montealtensis, Andrade & Bertini, 2008
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publication ID |
https://doi.org/ 10.11646/zootaxa.3686.2.4 |
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publication LSID |
lsid:zoobank.org:pub:9F87DAC0-E2BE-4282-A4F7-86258B0C8668 |
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DOI |
https://doi.org/10.5281/zenodo.6152134 |
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persistent identifier |
https://treatment.plazi.org/id/8B0487C7-FFE2-FD20-FF6A-FCA0A614FECF |
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treatment provided by |
Plazi |
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scientific name |
montealtensis |
| status |
comb. nov. |
Caipirasuchus montealtensis Andrade & Bertini, 2008 comb. nov.
Basionym: Sphagesaurus montealtensis Andrade & Bertini, 2008.
Holotype: MPMA 15-0001/90, the majority of the cranium and the anterior portion of the mandible ( Figs. 5 View FIGURE 5 , 6 View FIGURE 6 , 7 View FIGURE 7 ), from the municipality of Monte Alto, São Paulo State, Brazil.
Referred specimen. MPMA 68-0003/12, a nearly complete cranium and mandible ( Figs. 8 View FIGURE 8 , 9 View FIGURE 9 , 10 View FIGURE 10 ) and a posterior portion of the post-cranium, discovered in the municipality of Catanduva, São Paulo State.
Diagnosis. This species is diagnosed by the autapomorphic presence of a chamber that opens on the mesoventral wall of the pterygoids as a suboval opening. The antorbital fenestrae in this species are small and subcircular.
Remarks. The first studies of MPMA 15-0001/90 considered the general aspect of the cranium, and referred the specimen to the Uruguaysuchidae (Bertini 1993; Bertini & Arruda-Campos 1995; Bertini & Carvalho 1999; Andrade & Bertini 2003). Andrade et al. (2006) conducted a study of the choana, and observed several sphagesaurid features. Andrade & Bertini (2008) described the new species, Sphagesaurus montealtensis , which showed several synapomorphies with Sphagesaurus huenei.
Description. The unique teeth DGM 332-R and DGM 333-R provided the necessary data for the definition of a new genus and species and the diagnosis for the proposal of a new family ( Price, 1950; Kuhn; 1968). These “sphagesauriform” teeth (teeth with short triangular crowns covered by a relatively thick enamel layer, with a denticulate keel and longitudinal striae) are unique enough such that a diagnosis can still be applied to all family members; however, an emended diagnosis for the family is adopted here, based on the proposal by Iori et al. (2011), which considers a dental pattern observed in all species of the group in addition to the presence of sphagesauriform teeth. This pattern consists of the following: upper dentition where only the premaxillary teeth have a circular cross-section of the crown, while all teeth are sphagesauriform in the maxilla; for a premaxilla with at least two teeth, one hypertrophied caniniform tooth and one post-caniniform tooth with a conical crown and circular cross-section are required; a maxilla with six sphagesauriform, obliquely implanted teeth, except for the most posterior tooth which may present its long axis oriented perpendicularly to the sagittal axis; and dentary with six sphagesauriform posterior teeth, all obliquely implanted, except for the first tooth of the series, which may have its long axis anteroposteriorly oriented.
The variation in the teeth number in sphagesaurids occurs in the pre-caniniform teeth of the upper dentition and the anterior teeth of the lower dentition. Sphagesaurus shows an edentulous region between the caniniforms, as indicated for Caryonosuchus pricei ( Pol 2003; Kellner et al. 2011). Armadillosuchus has one pre-caniniform tooth in each premaxilla (Iori et al. 2011), while Caipirasuchus exhibits two. In the lower dentition, Caipirasuchus exhibits four anterior teeth (pre-sphagesauriform) in each dentary, while Sphagesaurus, Caryonosuchus and Armadillosuchus display three teeth ( Pol 2003; Marinho & Carvalho 2009, Iori & Carvalho 2011, Kellner et al. 2011).
In the holotype of Caipirasuchus montealtensis comb. nov. (MPMA 15-0001/90), the most anterior region of the rostrum is broken. Andrade & Bertini (2008) stated that the lost pre-maxillary region below the external nostril would be too shallow to support more teeth and posited an edentulous region between the caniniforms for the specimen, as is observed in Sphagesaurus huenei; however, Iori et al. (2011) noted that the left premaxilla, in the medial view, exhibits an alveolus in a longitudinal section located anteromedially to the caniniform alveolus, indicating a more numerous premaxillary dentition. Andrade & Bertini (2008) indicated that the first postcaniniform tooth of the Caipirasuchus montealtensis comb. nov. was an obliquely implanted maxillary tooth, but the premaxilla extends beyond the first post-caniniform tooth, which is a conical tooth with a circular cross-section. In larger sphagesaurids, such as Sphagesaurus and Armadillosuchus , it is possible to observe a posterior process of the premaxilla involving the first post-caniniform tooth, a structure that occurs in all members of the family; however, in smaller sphagesaurids, this projection is very narrow and delicate and can become difficult to identify. The Caipirasuchus montealtensis comb. nov. specimens had only the lateral and medial portions of this process preserved, indicating that the first post-caniniform alveolus opens in the premaxilla. Andrade & Bertini (2008) indicated a mandible with nine teeth in each dentary for the fossil MPMA 15-0001/90, with eight preserved pairs of teeth and one assumed pair, which would be procumbent and in the distal region of the mandible. The MPMA 68- 0003/ 12 specimen had all maxillary teeth preserved and implanted; however, all premaxillary alveoli were empty, only the right caniniform was preserved, the right dentary had eight preserved teeth and the left dentary had six preserved teeth. Even with several missing teeth, it is possible to determine that the dentition of Caipirasuchus montealtensis comb. nov. was composed with the same number of teeth as C. paulistanus , which has a premaxilla with four teeth, a maxilla with six teeth and a dentary with ten teeth. The shape and arrangement of the teeth are also similar in both species: the premaxilla exhibits two small teeth followed by one hypertrophied caniniform and one conical tooth, all with circular cross-sections and marked by longitudinal striae; the first three teeth of the dentary are small, conical, have a circular cross-section and have dorsally faced crowns; the fourth tooth is also conical, with a slightly oval cross-section and longitudinal striae; and the maxillary teeth and the last six teeth of the dentary follow the pattern observed for the entire family.
In general aspects, Caipirasuchus paulistanus and Caipirasuchus montealtensis comb. nov. have very similar crania and mandibles, and the bone arrangement is almost identical. The crania are narrow, with triangular shapes in the dorsal view, have a very peculiar ornamentation, are oreinirostral and have lateral orbits. It has been observed that in C. paulistanus , the cranium and mandible are higher than in Caipirasuchus montealtensis comb. nov., a characteristic that is mainly due to the arrangement of the ectopterygoid, palatine and pterygoid bones, the latter of which are very distinct between species.
Armadillosuchus, Sphagesauru s and Caryonosuchus are large sphagesaurids, with crania exceeding 250 mm in total length, while the Caipirasuchus crania do not grow over 180 mm in length. Regarding the general shape of the cranium, Caipirasuchus displays a longer rostrum and a more lanceolate dorsal outline, while in Armadillosuchus and Sphagesaurus the rostral regions are shorter and the transition between the rostrum and the posterior portion of the cranium is less smooth. Caipirasuchus displays a rostrum that makes up almost half the total cranium length and is relatively more narrow and longer than in Sphagesaurus and Armadillosuchus . In C. paulistanus the rostral narrowing is greater, more gradual and homogenous; the lateral and dorsal planes are nearly flat surfaces and the connection between both planes is marked by a conspicuous edge, while C. montealtensis comb. nov. shows a dorsolateral plane, making the transition between the lateral and dorsal planes, in addition to a lateral intumescence on the jugal line. Caipirasuchus has long nasal, separate from the external nostril; in C. paulistanus they are more anteriorly narrow and are only found on the dorsal and lateral surfaces, with the latter being in contact with the premaxilla and the maxilla (Iori & Carvalho 2011), while in Caipirasuchus montealtensis comb. nov. these contacts occur on the dorsolateral surface.
Sphagesaurids present a cranial ornamentation pattern, marked by irregular wrinkles and striae, which is present in almost the entire length of the cranium and lateral of the rostrum and jugal. Laterally, the region near the alveolar margin is smooth and marked by several neurovascular foramina ( Andrade & Bertini 2008; Pol 2003; Kellner et al. 2011; Iori & Carvalho 2011). Kellner et al. (2011) indicated the existence of semicircular grooves in Caryonosuchus, and ornamentations with such features are observed in Caipirasuchus montealtensis comb. nov. (MPMA 68-0003/12) in the squamosal region preceding the supratemporal fenestra. The medial portions of the parietal and the dorsal surface of the supraoccipital of the Caipirasuchus are highly ornamented. Moreover, the genus displays a small concavity on the posteromedial parietal region, a longitudinal crest in the frontal and a grooved region in the nasals that precedes and is parallel to the nasofrontal suture.
Among the five species of sphagesaurids described, the bone arrangement of the cranium is very similar, and the interspecies variations occur in the general shape of the cranium, the dental distribution and the presence or absence of certain structures. Some specific characters are observed in some members of the family, such as the rostral tubercles of Caryonosuchus and the presence of a cervical shield in Armadillosuchus (Kellner et al. 2011; Marinho & Carvalho 2009). Caipirasuchus exhibits antorbital fenestrae, unlike Sphagesaurus huenei and Armadillosuchus ( Pol 2003; Marinho & Carvalho 2009); in C. paulistanus , this fenestra is oval, dorsal-ventrally elongated and is bordered slightly by the jugal in its lower edge, while, in Caipirasuchus montealtensis comb. nov., this fenestra is small, circular and bordered only by the lacrimal and the maxilla. The chamber in the pterygoid was only observed in Caipirasuchus montealtensis comb. nov. (Iori & Carvalho 2011, Iori et al. 2012).
Only the holotype of C. paulistanus had completely preserved palpebrals. In both specimens of Caipirasuchus montealtensis comb. nov., only a small fragment of the anterior palpebrals was preserved; however, it is possible to observe a smooth region in the lateral margin of the frontal in specimen 68-0003/12, which indicates that there could have been a fenestra bordered by the frontal and the palpebrals, as with C. paulistanus .
Caipirasuchus paulistanus exhibits an external nostril bordered only by the premaxillae; an anterodorsal process of the maxilla makes contact with the nasal, excluding them from the external nostril margin. In Sphagesaurus huenei, the nasals participate in the margin slightly. Andrade & Bertini (2008) propose that the same would happen with the MPMA 15-0001/ 90 specimen; however, this region is not preserved in this fossil. Caipirasuchus montealtensis comb. nov. (MPMA 68-0003/12) shows a remnant of the anterodorsal process of the premaxilla, which most likely also excludes the nasal from the external nostril margin because the distal portions of the nasals exhibit suture marks. An anteroventral process of the premaxilla is also observed in Caipirasuchus montealtensis comb. nov. (MPMA 68-0003/12), as indicated by Pol (2003) for S. huenei. The presence of the anterior processes of the premaxillae in sphagesaurids allows us to consider the possible existence of an internarial bar in members of the family, as occurs in most Notosuchia.
The fossils of Armadillosuchus, Caryonosuchus and Sphagesaurus do not have preserved choanae, while the specimens of the genus Caipirasuchus have these regions almost intact, with fossil MPMA 68-0003/12 of Caipirasuchus montealtensis comb. nov. being the best preserved. The proximal halves of the palatines border the nasopharyngeal duct, laterally and ventrally. The opening of this duct is located at the beginning of the lateral deflection of the palatines. A small medial process of the palatine extends from this point and contacts a large anterior process of the pterygoid, forming a tubular structure, noted by Andrade & Bertini (2008) as an interchoanal septum. A fenestra is formed laterally to this bar, bounded by the deflected bar of the palatine and by the pterygoid. Caipirasuchus presents the internal nostril opening caudally, unlike most of the crocodylomorphs, where the choana opens ventrally. The medial regions of the pterygoids differ greatly among the species of Caipirasuchus. In C. paulistanus , these regions are smooth and closed, while C. montealtensis comb. nov. displays a chamber opening in this bone. This opening is wide and occupies approximately half of the medioventral surface of the pterygoid. The chamber occupies the entire distal portion of the pterygoid; a foramen opens dorsally in the pterygoid chamber. There may be a pneumatic connection between the nasopharyngeal duct, the interchoanal septum and the chamber of the pterygoid.
The main autapomorphies of the genus Caipirasuchus are as follows: the presence of an antorbital fenestra, an external nostril bordered only by the premaxillae and a premaxilla with four teeth. Structurally, C. paulistanus has a higher cranium and a narrower rostrum, whereas Caipirasuchus montealtensis comb. nov. exhibited a lower cranium and mandible, providing a more robust aspect to this taxon. The cranial roof of specimen MPMA 68-0003/ 12 collapsed during fossilization, but some morphometric data could still be measured. It was noted that both specimens of Caipirasuchus montealtensis comb. nov. showed similar measurements and differed from C. paulistanus by presenting the following characteristics: a larger rostral width at the line of the caniniforms; a lower mandibular height, both in the anterior region of the mandibular fenestra and at the highest point of the symphysis; and, in C. paulistanus , the distal ends of the ectopterygoids and proximal ends of the pterygoids project more ventrally than in Caipirasuchus montealtensis comb. nov. ( Fig. 11 View FIGURE 11 ). This projection results in a more acute angle formed between the mandible plane and the suborbital fenestrae plane in C. paulistanus compared to that in Caipirasuchus montealtensis comb. nov. (135º for C. paulistanus and approximately 147º for Caipirasuchus montealtensis comb. nov.) (Iori & Carvalho 2011). The most striking aspect that differentiates these two species is the pterygoid chamber, which is present in Caipirasuchus montealtensis comb. nov. and absent in C. paulistanus .
The holotype of C. paulistanus did not have the dorsal region of the articular preserved, but, in the MPMA 68- 0003/ 12 specimen of Caipirasuchus montealtensis comb. nov., an anteroposteriorly expanded protuberance in the articular region with the quadrate was observed, which allows anteroposterior sliding of the mandible. This arrangement in the craniomandibular articulation must be present in the other sphagesaurids because it would contribute to the propalinal movement noted in several studies with members of the family ( Pol 2003; Marinho & Carvalho 2009; Iori & Carvalho 2011).
Iori & Carvalho (2011) presented a phylogenetic analysis, where Sphagesaurus montealtensis (Caipirasuchus montealtensis comb. nov.) appears to be a sister species to Armadillosuchus ; however, in that study, the data used were from a holotype (MPMA 15-0001/90) with an incomplete cranium and mandible. In the present study, a different specimen (MPMA 68-0003/12) was used to provide data on the cranial and post-cranial characters that were not preserved in the previous holotype. The results indicate that Caipirasuchus paulistanus and Caipirasuchus montealtensis comb. nov. are sister species among Sphagesauridae , corroborating what is proposed in the present study.
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