Trematochampsa, TAQUETI BUFFETAUT, 1974

Meunier, Louise M V & Larsson, Hans C E, 2018, Trematochampsa taqueti as a nomen dubium and the crocodyliform diversity of the Upper Cretaceous In Beceten Formation of Niger, Zoological Journal of the Linnean Society 182 (3), pp. 659-680 : 662-664

TREMATOCHAMPSA TAQUETI BUFFETAUT, 1974

( FIG. 2A–H )

Holotype: Ibc 231, isolated right lacrimal ( Fig. 2C–H )

Reducing Trematochampsa taqueti to a nomen dubium: The type of T. taqueti is an isolated right lacrimal, Ibc 231 ( Fig. 2C–H ). We propose the taxon T. taqueti be reduced to a nomen dubium based on the following description and discussion of this specimen that can find no morphologies to diagnose this taxon from other known crocodyliforms. Furthermore, because the type is a single isolated element, neither associated nor confidently combined with any other material in the In Becetin crocodyliform collection, nothing from this collection can be assigned to T. taqueti as a lectotype.

The lacrimal Ibc 231 was described by Buffetaut in 1974 and 1976. The original diagnostic morphologies of T. taqueti that were present on the holotype are only the presence of a large antorbital fenestra on the lacrimal and maxilla and, by inference, a relatively small to medium body size (1–3 m) of the animal. The fenestra is relatively small, but the fossa is large. Both these morphologies are present in many small- to mediumsized Crocodyliformes and do not constitute unique diagnostic morphologies for T. taqueti .

Anteriorly, Ibc 231 has a large antorbital fossa that expands well beyond a small antorbital fenestra that is defined by a small circular edge on the anterodorsal margin of the lacrimal. Although the entire fenestra is not preserved because it would have been bounded also by the maxilla, the acute circumference of the bor- der on the lacrimal suggests the fenestra was small. The fossa expands ventrally to the maxilla contact and dorsally to a broken edge. The ventral edge of the fossa is marked by a low but distinct near horizontal ridge that may have been the external limit to the maxillary contact. Below this ridge, the lacrimal is relatively smooth and lightly textured, possibly to contact a thin superficial overlap from the maxilla. A similar ventral antorbital fenestra morphology is present in Uberabasuchus terrificus and Montealtosuchus arrudacamposi . This morphology suggests the antorbital fossa extended ventrally onto the maxilla. The remain- der of the external surface of the lacrimal is heavily ornamented anteroventrally with pitting and sulci extending onto the orbital margin. The posterior margin of the antorbital fenestra is sharply edged with the fossa placed deep from the lacrimal superficial surface, creating a sharp bony roof on the posterior margin of the fossa. This type of deeply inset antorbital fossa and ornamented orbital margin of the lacrimal is only otherwise present in U. terrificus and Mo. arrudacamposi .

The posteroventral corner of the lacrimal has a large, complex, ovate suture that contacted the jugal. The robust jugal contact posteroventrally and slender maxilla contact anteroventrally is shared with many Crocodyliformes, such as Araripesuchus (all species), Sebecia and Neosuchia . However, many notosuchians, including Malawisuchus and derived notosuchians (following Pol et al., 2014), lack a lacrimal–jugal contact implying no relationship to these taxa. The jugal and maxilla contact at the lacrimal of T. taqueti compares closest to Araripesuchus wegeneri , U. terrificus and Mo. arrudacamposi , with a robust butt lacrimal–jugal contact and a thin lacrimal–maxilla overlapping contact with the antorbital fossa extending onto the maxilla.

Dorsolaterally, the lacrimal is deeply ornamented and forms a sharp posterior edge to the antorbital fossa. The fossa is smooth and the lacrimal portion of the fossa bounds the posteroventral corner of a small antorbital fenestra. The lateral surface of the lacrimal is relatively straight in posterior aspect. The robust prefrontal suture occupies much of the posterodorsal and posterodorsomedial surfaces of the lacrimal. Medially, a low, horizontal crest extends anteriorly from the base of the prefrontal contact and another smaller crest parallels this crest anterodorsally. A large lacrimal duct pierces the dorsal orbital margin and appears to have been bordered dorsally by the prefrontal. Two smaller foramina lie medial to the lacrimal duct.

Many of these morphologies are present in U. terrificus , Mo. arrudacamposi , An. minor and Ar. wegeneri , but not in other Araripesuchus species. Specifically, the topology of bones surrounding the antorbital fenestra is shared with these taxa. Differences with Uberabasuchus include the vertically oriented lacrimal edge to the antorbital fossa, as opposed to the curving, posteroventral margin in Ibc 231. Additionally, the orbital margin on the lacrimal of Uberabasuchus is linear with an angular dorsal margin, whereas the orbital margin in Ibc 231 is gently concave. Differences with Anatosuchus include the lack of ornamentation and relatively narrow proportions in this taxon’s lacrimal bar. There are few differences with Ar. wegeneri , but one notable difference is the lack of a sharp-edged and roofing posteroventral margin of the antorbital fenestra. However, the posterior sharp and roofed edge of the antorbital fossa, ornamentation and orbital margin is nearly identical to Mo. arrudacamposi . In fact, close examination of both finds no diagnostic features to separate the two. All morphologies described above for Ibc 231 are also present in the lacrimal of Mo. arrudacamposi . Therefore, in light of these more recent crocodyliform discoveries, we find no autapomorphies for Ibc 231.

Figures

Figure 2. Trematochampsa taqueti. Original cranial reconstruction modified from Buffetaut (1976) in (A) lateral and (B) dorsal views. Right lacrimal Ibc 231, holotype of T. taqueti in (C) lateral, (D) posterior and (E) medial view. F, G, H, outline drawings corresponding to each view. Montealtosuchus arrudacamposi in (F) left lateral and (K) close-up on the lacrimal region. J, L, outline drawings corresponding to each view. Abbreviations: antfe, antorbital fenestra; antfo, antorbital fossa; fo, foramen; j.s, suture for jugal; m.s, maxilla suture; mt, maxilla tooth; pf.s, suture for prefrontal. Scales are 1 cm.