A Southern Tyrant Reptile

Abstract

Fossil evidence indicates that tyrannosaurs also inhabited the southern continents in the late Early Cretaceous period.

Phylogenetic relationships of the Cretaceous Gondwanan theropods Megaraptor and Australovenator: the evidence afforded by their manual anatomy

“…Additional evidence of the presence of megaraptorids in regions of South America other than Argentina comes from Brazil, from which isolated caudal vertebrae have been described (Mendez et al, 2013). Cretaceous formations of Australia have yielded several isolated elements referred to Megaraptoridae, including Rapator ornitholestoides (Huene, 1932;Agnolín et al, 2010;White et al, 2012), an isolated ulna closely similar to that of Megaraptor and Australovenator (Smith et al, 2008), more than one hundred isolated teeth (Benson et al, 2012), and probably an isolated astragalus (Molnar et al, 1981;Fitzgerald et al, 2012), and paired pubes originally described as tyrannosauroid (Benson et al, 2010b;Novas et al, 2013).…”

Comment on “A Southern Tyrant Reptile”

“…Given the presence of a transversely narrow pubic boot (8), we accept the possibility that NMV P186046 is referable to Coelurosauria (1); however, as we are uncertain of the degree of bone loss from the ventral pubic boot [in agreement with Benson et al (1) that the pubic boot is broken], we only tentatively acknowledge this referral. Furthermore, the broader distribution among neotetanurans of the other pubic boot traits identified in NMV P186046 (1) indicates that a more inclusive neotetanuran placement would be more parsimonious.…”

“…1A). Benson et al (1) consider this morphology diagnostic of tyrannosaurids and dromaeosaurids following previous studies (3,4). According to Benson et al [ figure 1B in (1)], a shadowed groove on NMV P186046 represents the broken base of the pubic tubercle.…”

“…enson et al (1) reported the presence of "a southern tyrant reptile"-the first tyrannosauroid theropod dinosaur from Gondwana. This finding, based on an isolated pair of fused pubic bones [National Museum of Victoria (NMV) P186046] from the Early Cretaceous of Victoria, southeastern Australia, has profound implications for tyrannosauroid evolution and paleobiogeography.…”

“…Three character states of the pubic boot were identified by Benson et al (1) in NMV P186046: a narrowly transverse, parallel-sided pubic boot; an anteroposteriorly large pubic boot; and a lengthy anterior expansion of the pubic boot. A narrowly transverse, parallel-sided pubic boot is considered a coelurosaurian synapomorphy (8) …”