Purussaurus mirandai Aguilera, Riff, and Bocquentin Villanueva, 2006

Scheyer, TM & Delfino, M, 2016, The late Miocene caimanine fauna (Crocodylia: Alligatoroidea) of the Urumaco Formation, Venezuela, Palaeontologia Electronica 176 (4), pp. 1-57 : 31

Purussaurus mirandai Aguilera, Riff, and Bocquentin Villanueva, 2006

The type species of Purussaurus , P. brasiliensis , was described based on the anterior portion of a right mandibular ramus from the Miocene Solimões Formation, Acre, Brazil (Barbosa-Rodrigues, 1892). More complete cranial and mandibular material from this formation was later described and figured (Aguilera et al., 2006; Aureliano et al., 2015). Besides P. brasiliensis , two more species were described, P. neivensis from the middle Miocene, La Venta fauna, Colombia ( Mook, 1941; Langston, 1965) and the Pebas system of Peru ( Salas-Gismondi et al., 2015), and P. mirandai from the Urumaco Formation, Venezuela (Aguilera et al., 2006).

To date, only a single species, Purussaurus mirandai , is recognised in the Urumaco Formation (Aguilera et al., 2006; Sánchez-Villagra and Aguilera, 2006; Riff et al., 2010; Scheyer et al., 2013). Besides the cranial and mandibular remains used in the original description (of the holotype UNEFM- CIAAP-1369, Figure 24.1-5 ; paratypes UNEFM- CIAAP-1445, Figure 24.6 ; AMU-CURS-135, Figure 24.7 , MCNC-URU-115-72V, Figure 25.1 ; MCNC- URU-157-72V; referred material AMU-CURS-033 and -057; MCNC-URU-76-72V), several other Purussaurus specimens including cranial remains are stored in the collections in Urumaco, Coro, and Caracas or have since been discovered in the field. It is difficult in many cases, however, to identify isolated specimens down to the species level.

MCNC-URU-115-72V constitutes the anterior portion of a right dentary ( Figure 25.1 ). This dentary fragment preserves the anterior nine and a half alveoli, the fourth alveolus being 46 mm in diameter. It was apparently found close to specimen MCNC-URU-112-72V, associated cranial and mandibular material that was both heavily and falsely reconstructed with plaster, which, following Aguilera et al. (2006, page 230) is excluded herein.

A right premaxilla and maxilla shown in ventral view, instead of the aforementioned right dentary, was presented by Aguilera et al. (2006) as paratype material (as ‘MCC URU-115-72V’: Aguilera et al., 2006, figure 3B). These bones are part of a more complete cranial specimen, accompanied by the left premaxilla and maxilla, as was shown previously in Aguilera (2004, page 91). The remains from the left side of the skull could be relocated and have been virtually assembled to their life position in Figure 25.2-3 , which is some degrees wider than previously indicated (Aguilera, 2004), forming a round snout shape. The premaxillae are huge, flat, and carry a prominent posterior process framing a huge external narial opening, thus allowing assignment of the material to Purussaurus mirandai . We hypothesise that all skull fragments ( Figure 25.2-4 ) belong to MCNC-URU-158- 72V (see discussion below), together with more posterior skull parts, including a partial skull table, a jugal, the pterygoids (?), an ectopterygoid, and the quadrates ( Figure 25.5-21 ). On the other hand, it is noteworthy that at least one other, smaller skull fragment ( Figure 25.22 ) assignable to Purussaurus was accessioned under the same number (two small caimanine skulls, not shown in the figures, are also within this assemblage). Furthermore, two lower dentary fragments lacking documentation ( Figure 25.23 ) likely belong to MCNC-URU-158- 72V as well. The fragments show the symphyseal region, which was measured to be 21 cm in anteroposterior length. The left dentary has nine alveoli preserved, whereas 17 alveoli are preserved on the right dentary fragment. The diameter of the first alveolus is about 6 cm.

Figures

FIGURE 24. Photographs of skull of holotype (1-5: UNEFM-CIAAP-1369; associated lower jaw not shown) and paratypes UNEFM-CIAAP 1445 (6) and AMU-CURS-135 (7) of Purussaurus mirandai. 1-3, holotype skull in dorsal (1), ventral (2) and angled rostral view (3); the latter is not to scale. 4, 5, skull fragment labelled as “quadrate” of UNEFM-CIAAP-1369, which possibly constitutes a proximal fragment of the left quadrate/quadratojugal complex of the holotype skull. 6, right lower jaw in dorsal view. 7, largely unprepared skull and attached left and right lower jaw rami in dorsal view (picture courtesy: Jorge Moreno, Colombia).

FIGURE 25. Photographs of skull and jaw material of Purussaurus. 1, right dentary fragment (MCNC-URU-115-72V) in dorsal view; 2-23, skull and lower jaw material belonging to several different individuals currently accessioned under a single collection number (MCNC-URU-158-72V). 2-3, anterior part of skull (electronically assembled to represent life position) in dorsal and ventral view. Only the right premaxilla and maxilla (2-4) were shown as part of the paratype series of P. mirandai by (Aguilera et al., 2006). 5, right part of skull table in dorsal view. 6, left part of skull table in lateral view. 7, isolated tooth. 8, 9, left quadrate in dorsal and ventral view. 10, right quadrate in dorsal view. 11, right ectopterygoid in posterolateral view. 12, lower jaw fragment in medial view with alveoli. 13, right jugal in lateral view. 14, 15, articulars with retroarticular processes in dorsal view. 16, 17, pterygoids? 18-21, lower jaw elements. 18, possible anterior fragment of left surangular in ventral view? 19, posterior fragment of surangular in lateral view? 20, fragment of right angular in medial view? 21, fragment of right surangular in medial view? 22, smaller skull table in the assemblage also assignable to Purussaurus in dorsal view. 23, anterior portion of lower jaw, initially referred to and figured as MCNC-URU-157-72V by (Aguilera, 2004).