Andesaurus, Heterodontosaurus, and new Cormorants

[Jaime Headden <qi_leong@hotmail.com>]

  Today sees the publication of three papers, two of which were held in the OBP 
system of _Zoological Journal of the Linnaean Society_. I've remarked before 
about my reluctance to talk about unpublished papers, even if they do not 
involve new taxonomy. To me, this extends to the casual paper. In one of the 
papers listed below, "new" taxonomy is not introduced, but it revises "current" 
taxonomy in several instances, which I am just as wary about, because these 
things become cited just as others do. Anyways,

A Basic Titanosaur

Mannion, Philip D. & Calvo, Jorge, O. 2011. Anatomy of the basal titanosaur 
(Dinosauria, Sauropoda) *Andesaurus delgadoi* from the mid-Cretaceous 
(Albian--early Cenomanian) Río Limay Formation, Neuquén Province, Argentina: 
Implications for titanosaur systematics. _Zoological Journal of the Linnaean 
Society_ 163(1):155-181.
http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2011.00699.x/abstract

Abstract:
"Titanosauria is a taxonomically and morphologically diverse clade of sauropod 
dinosaurs that appeared in the Middle Jurassic and radiated in the mid–Late 
Cretaceous; however, its intrarelationships are poorly understood. The 
mid-Cretaceous Argentinean sauropod *Andesaurus delgadoi* has repeatedly been 
recovered at the base of Titanosauria, and thus represents a crucial taxon for 
determining the evolutionary history of this clade; yet it has only received a 
brief description. Here, we re-describe the holotype, comprising dorsal, 
sacral, and caudal vertebrae, as well as limb and pelvic elements. Detailed 
comparisons are made with a global array of titanosauriforms. *Andesaurus* is a 
valid genus and can be diagnosed by five autapomorphies: (1) posterior dorsal 
neural spine height greater than twice centrum height (autapomorphic within 
Macronaria); (2) square-shaped anterior–middle caudal centra in lateral view; 
(3) anteroposteriorly elongate fossa present on the anterodorsal corner of the 
lateral surface of middle–posterior caudal centra; (4) ridge along the midshaft 
of the ventral surface of metacarpal I, close to the ventromedial margin; (5) 
prominent ventromedial ridge along the distal half of metacarpal V. Other 
remains previously attributed to *Andesaurus* cannot be referred to this genus. 
Sixteen putative titanosaur synapomorphies can be recognized in *Andesaurus,* 
including: (1) lateral pneumatic foramina in dorsal vertebrae situated within 
fossae; (2) anterior–middle caudal vertebrae with ventrolateral ridges either 
side of a ventral midline hollow; and (3) lateral bowing of metacarpal I. This 
revision provides an important foundation for future phylogenetic analyses of 
titanosaurs, and adds to our growing understanding of this enigmatic clade. 
Lastly, we recommend the disuse of the coordinated suprageneric rank taxa of 
*Andesaurus* (Andesaurinae, Andesauridae, and Andesauroidea), at least until 
titanosaur intrarelationships are better elucidated."

--
Sabre-Toothed Dinosaurs

I had previously implied some knowledge of this paper when I posted this:
http://qilong.wordpress.com/2011/05/20/bloody-gorgeous/

Following my otherwise inane fascination with things reptilian and heterodont 
-- and its defiance of the old-order argument that reptiles all had "simple" 
teeth -- I'd followed the argument that others have proposed that 
heterodontosaurs in general represented the _basal_ condition of a clade of 
taxa for which relatively homogenous dentition arose, namely 
*Pachycephalosauria* and *Ceratopsia*. To that end, I posted this:
http://qilong.wordpress.com/2010/06/19/sabre-toothed-dinosaurs/

Norman et al. present an analysis, and one of the most extensive to date 
regarding both the character transformation and phylogenetic placement of, 
*Heterodontosaurus tucki*. It includes a discussion of the many phylogenetic 
positions proposed for heterodontosaurids, and thus the placement alongside or 
anywhere near marginocephalians. I have a response to that particular element 
of the paper, but would like to reiterate that this paper is _bloody brilliant_ 
and tip my hat to the authors in placing a high benchmark for any potential 
responses or results-based analyses in regards to the controversial placement 
of heterodontosaurs in general. They place the hets in the base of 
*Ornithischia*, a position that has become increasingly viable due in large 
part to Richard Butler flooding basal ornithischian analyses with new and 
better character data. I do not disagree with them, because I have no better 
solution, but I decided to analyze their arguments regarding character value in 
contradictory, and this involves my latest post:
http://qilong.wordpress.com/2011/08/19/sabretooths-spread-thick-and-thin/

Norman, David B., Crompton, Alfred W., Butler, Richard J., Porro, Laura B. & 
Charig, Alan J. 2011. The Lower Jurassic ornithischian dinosaur 
*Heterodontosaurus tucki* Crompton & Charig, 1962: Cranial anatomy, functional 
morphology, taxonomy, and relationships. _Zoological Journal of the Linnaean 
Society_ 163(1):182-276.
http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2011.00697.x/abstract

Abstract:
"The cranial anatomy of the Lower Jurassic ornithischian dinosaur 
Heterodontosaurus tucki Crompton & Charig, 1962 is described in detail for the 
first time on the basis of two principal specimens: the holotype (SAM-PK-K337) 
and referred skull (SAM-PK-K1332). In addition several other specimens that 
have a bearing on the interpretation of the anatomy and biology of 
*Heterodontosaurus* are described. The skull and lower jaw of 
*Heterodontosaurus* are compact and robust but perhaps most notable for the 
heterodont dentition that merited the generic name. Details of the cranial 
anatomy are revealed and show that the skull is unexpectedly specialized in 
such an early representative of the Ornithischia, including: the closely 
packed, hypsodont crowns and ‘warping’ of the occlusal surfaces (created by 
progressive variation in the angulation of wear on successive crowns) seen in 
the cheek dentition; the unusual sutural relationships between the bones along 
the dorsal edge of the lower jaw; the very narrow, deeply vaulted palate and 
associated structures on the side wall of the braincase; and the indications of 
cranial pneumatism (more commonly seen in basal archosaurs and saurischian 
dinosaurs). Evidence for tooth replacement (which has long been recognized, 
despite frequent statements to the contrary) is suggestive of an episodic, 
rather than continuous, style of tooth replacement that is, yet again, unusual 
in diapsids generally and particularly so amongst ornithischian dinosaurs. 
Cranial musculature has been reconstructed and seems to conform to that 
typically seen in diapsids, with the exception of the encroachment of M. 
adductor mandibulae externus superficialis across the lateral surface of the 
temporal region and external surface of the lower jaw. Indications, taken from 
the unusual shape of the occlusal surfaces of the cheek dentition and jaw 
musculature, are suggestive of a novel form of jaw action in this dinosaur. The 
taxonomy of currently known late Karoo-aged heterodontosaurids from southern 
Africa i!
s reviewe
cated by the inadequate nature of much of the known material, it is concluded 
that two taxa may be readily recognized: *H. tucki* and *Abrictosaurus 
consors.* At least one additional taxon is recognized within the taxa presently 
named *Lanasaurus* and *Lycorhinus*; however, both remain taxonomically 
problematic and their status needs to be further tested and may only be 
resolved by future discoveries. The only other named taxon, Geranosaurus 
atavus, represents an invalid name. The recognition of at least four distinct 
taxa indicates that the heterodontosaurids were speciose within the late Karoo 
ecosystem. The systematics of *Heterodontosaurus* and its congeners has been 
analysed, using a restricted sample of taxa. A basal (nongenasaurian) position 
within Ornithischia is re-affirmed. There are at least four competing 
hypotheses concerning the phylogenetic placement of the Heterodontosauridae, so 
the evidence in support of the various hypotheses is reviewed in some detail. 
At present the best-supported hypothesis is the one which places 
Heterodontosauridae in a basal (non-genasaurian) position; however, the 
evidence is not fully conclusive and further information is still needed in 
respect of the anatomy of proximate outgroups, as well as more complete 
anatomical details for other heterodontosaurids. Heterodontosaurids were not 
such rare components of the late Karoo ecosystem as previously thought; 
evidence also suggests that from a phylogenetic perspective they occupied a 
potentially crucial position during the earliest phases of ornithischian 
dinosaur evolution."

--
New phalacrocoracids!

Worthy, Trevor H. 2011. Descriptions and phylogenetic relationships of a new 
genus and two new species of Oligo-Miocene cormorants (Aves: Phalacrocoracidae) 
from Australia. _Zoological Journal of the Linnaean Society_ 163(1):277-314.
http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2011.00693.x/abstract

Abstract:
"Tertiary cormorant fossils (Aves: Phalacrocoracidae) from Late Oligocene 
deposits in Australia are described. They derive from the Late Oligocene – 
Early Miocene (26–24 Mya) Etadunna and Namba Formations in the Lake Eyre and 
Lake Frome Basins, South Australia, respectively. A new genus, *Nambashag* gen. 
nov., with two new species (*Nambashag billerooensis* sp. nov., 30 specimens; 
*Nambashag microglaucus* sp. nov., 14 specimens), has been established. 
Phylogenetic analyses based on 113 morphological and two integumentary 
characters indicated that *Nambashag* is the sister taxon to the Early Miocene 
*Nectornis miocaenus* of Europe and all extant phalacrocoracids. As 
*Nambashag*, *Nectornis*, and extant phalacrocoracids constitute a strongly 
supported clade sister to *Anhinga* species, the fossil taxa have been referred 
to Phalacrocoracidae. Sulids and Fregata were successive sister taxa to the 
Phalacrocoracoidea, i.e. phalacrocoracids + *Anhinga*. As phalacrocoracids 
lived in both Europe and Australia during the Late Oligocene and no older 
phalacrocoracid taxa are known, the biogeographical origin of cormorants 
remains unanswered. The phylogenetic relationships of extant taxa were not 
wholly resolved, but contrary to previous morphological analyses, considerable 
concordance was found with relationships recovered by recent molecular 
analyses. *Microcarbo* is sister to all other extant phalacrocoracids, and all 
*Leucocarbo* species form a well-supported clade." 



Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)