Deinonychus antirrhopus (Ostrom, 1969)

Brownstein, Chase Doran, 2021, Dromaeosaurid crania demonstrate the progressive loss of facial pneumaticity in coelurosaurian dinosaurs, Zoological Journal of the Linnean Society 191 (1), pp. 87-112 : 94-95

Deinonychus antirrhopus

Only a partial right lacrimal is known for Deinonychus antirrhopus ( Ostrom, 1969; Turner et al., 2012). Ostrom (1969) described the pneumatic fenestra situated in the posterodorsal corner of the antorbital fossa in this bone, which seems to have been reduced relative to Velociraptor , Tsaagan and other dromaeosaurids [see Turner et al. (2012) for additional figs]. Ostrom (1969) briefly describes the morphology of this bone, and so I refer the reader to that paper for further anatomical description of the element.

Velociraptor

The lacrimal of Velociraptor is highly pneumatic ( Fig. 2A–B ), with several large pneumatic foramina and the dorsoposteriorly located pneumatic fenestra leading into the lacrimal sinus as in other theropods ( Witmer, 1997; Witmer & Ridgely, 2008; Tahara & Larsson, 2011; Gold et al., 2013). These include a row of pneumatic foramina in the antorbital fossa of the bone that lead up to the large pneumatic fenestra, which is concealed by the rim of the antorbital fossa as in other coelurosaurs (e.g. Tahara & Larsson, 2011; Gold et al., 2013). These are large, ovoid structures ( Fig. 2A–B ). In addition to these pneumatic features within the antorbital fossa, the lacrimal of Velociraptor also bears several neurovascular foramina on its dorsal surface. One of the lacrimals of the holotype of Velociraptor is broken, revealing the internal hollow space for the lacrimal sinus. The space for the lacrimal sinus clearly extends caudally into the caudal ramus of the lacrimal, as in tyrannosaurs ( Gold et al., 2013). The lacrimal sinus also probably extended into the dorsal ramus of the lacrimal as well, although this feature is difficult to see in the holotype.

Figures

Figure 2. Craniofacial pneumaticity of Velociraptor. Skull AMNH FARB 6515 in (A, C) lateral and (B, D) medial views, with the rostrum in (E) lateral and (F) medial views. Abbreviations: aofen, antorbital fenestra; aof, antorbital fossa; mf, maxillary fenestra; mx, maxilla; pmf, promaxillary fenestra; mi, maxilla interior;?pipf, premaxillary pneumatic foramina; pmx, premaxilla; pf, pneumatic foramina of the frontal; front, frontal; nf, neurovascular foramina; rugose, rugose bone surface; smooth, smooth bone surface. In (C) and (D), light blue are neurovascular foramina, light green is the maxillary fenestra, light red is the promaxillary fenestra, tan is an additional maxillary fenestra.