RE: Razanandrongobe sakalavae

[Tim Williams <twilliams_alpha@hotmail.com>]

Marco Auditore wrote:

> Maganuco S., Dal Sasso C., and Pasini G., 2006 - A new large predatory 
> archosaur from the Middle Jurassic of Madagascar, with remarks on its 
> affinities and paleobiology. Atti della Società Italiana di Scienze 
> Naturali e del Museo Civico di Storia Naturale in Milano, 147 (I): 19-51.

The material comes from the Isalo IIIb subunit of the Mahajunga basin, dated 
to Bathonian, near Ambondromamy in NW Madagascar.

"Systematic Paleontology
Archosauromorpha Huene, 1946
Archosauriformes Gauthier, Kluge & Rowe, 1988
Archosauria Cope, 1869 sensu Gauthier, 1986
_Razanandrongobe sakalavae_, gen. et sp. nov.

Holotype: MSNM V5770 Fragmentary right maxilla bearing three unerupted 
teeth.
Referred material: MSNM V5771-5777, isolated teeth.

Etymology: _Razanandrongobe_, Malagasy composite name for ?ancestor? 
(Razana-) of the ?large? (-be) ?lizard? (-androngo-); sakalavae, Latin for 
?of Sakalava?, the ethnic group that inhabits the Mahajanga region.

Diagnosis: large predatory archosaur with deep, robust maxilla bearing a 
prominent maxillary medial shelf; thecodont tooth implantation; alveolar 
channels nearly straight in the sagittal plane; alveoli (as preserved) 
sub-rectangular in ventral view; fused interdental plates with a surface 
texture consisting of marked ridges and furrows extending for a short 
distance also above the dorsal margin of the interdental plates; heterodont 
dentition; incisiform rostral teeth, U-shaped in cross-section; stout 
lateral teeth, sub-oval in cross-section; smallest lateral teeth, 
globe-shaped; denticles present on both carinae in all the teeth, and very 
large (0.8- 1.4 per mm) (unambiguous autapomorphy of the taxon)."

The paper goes on to say that _Razanandrongobe_ is either a crocodylomorph 
or a theropod ("Although _R. sakalavae_ differs in some aspects from any 
currently known member of the Crocodylomorpha and Theropoda, it belongs 
certainly to one of those two taxa.")  The preserved maxillary fragment is 
192 mm long, 124 mm high, and 96 mm wide, and the authors suggest that 
_Razanandrongobe_ might have been of a similar size to either _Sarcosuchus_  
(if a crocodylomorph) or _Daspletosaurus_ (if a theropod).  In other words, 
pretty darn big either way.  _Razanandrongobe_ was clearly a carnivore, with 
the teething show some similarities to those of tyrannosaurids (but not 
enough to indicate a close phylogenetic relationship, just a similar mode of 
predatory behavior), and indicating it could chomp on bone and tendons.  
_Razanandrongobe_ may have fed on sympatric sauropods such as 
_Lapparentosaurus_ and _Archaeodontosaurus_, say the authors.

Thanks to Simon Maganuco for a copy of the paper.

> Abstract ­ Here we report on the finding of new vertebrate remains from the 
> Middle Jurassic (Bathonian) of the Mahajanga basin, NW Madagascar, that 
> represent one of the largest predatory archosaurs from Gondwana. The 
> remains consist of a fragmentary right maxilla bearing three teeth and 
> seven isolated teeth that clearly belong to a single taxon. Although the 
> scarcity of the remains renders
> establishment of affinities difficult, the presence of a unique combination 
> of features including a well developed medial shelf of the maxilla, rostral 
> and lateral teeth respectively U-shaped and sub-oval in cross-section, and 
> very large tooth denticles (1 per mm), allows us to erect a new taxon, 
> Razanandrongobe
> sakalavae. Additionally, the structure of the teeth, the peculiar wear of 
> their enamel, and the morphology of the maxilla strongly suggest that 
> Razanandrongobe sakalavae often crushed the bones of its prey.