Re: Protopenguins and pterosaurs

[David Marjanovic <david.marjanovic@gmx.at>]

> That's-
> Cambra-Moo et al., in press. Histological observations of enantiornithine
> bone (Saurischia, Aves) from the Lower Cretaceous of Las Hoyas (Spain).
> Comptes Rendus Palevol.
> The pdf is available online.  The specimen is a partial leg.

Ah. I don't have access (yet), but here's the abstract:

"New material from a small, presumably adult enantiornithine bird 
(Saurischia: Aves) from the Lower Cretaceous of Las Hoyas (Spain) provides 
new data on the bone histology of those Mesozoic birds, which became extinct 
at the Cretaceous-Tertiary boundary. The material is referred to cf. 
*Concornis lacustris*. The outer cortex of the studied long bones is formed 
of a rather typical parallel-fibered bone tissue, with sparse flattened 
osteocyte lacunae, evidence of lines of arrested growth (LAGs) and no 
vascularization. This structure matches the outer circumferential layer 
(OCL) of many extant mature, small to tiny birds and also agrees with 
earlier descriptions of enantiornithine cortical bone. The deeper cortex 
progressively contains a much more plentiful component of osteocyte lacunae, 
which are more plump than flat. This region is also permeated by a few 
vascular canals surrounded by bone lamellae that form osteonal structures. 
The relationship of the osteonal material to the neighbouring primary tissue 
strongly suggests that the osteons are secondary. In some sections, it is 
possible to follow those osteons as formed by outward extensions from the 
endosteal bone tissue into the deep primary cortex. This specimen shows more 
histodiversity than the few enantiornithine samples previously reported. 
This further suggests that although growth may have been slow when the adult 
size was approached, it was more rapid at earlier stages. Even if as yet not 
enough is known of those early stages to document just how rapid early 
growth may have been, and whether enantiornithines grew differently from the 
basal avian models known from other early birds, the new data do not 
necessarily suggest that they had growth regimes quite distinct from extant 
birds of similar body sizes nor, by implication, completely different 
metabolic patterns or regimes."

> I was surprised to see just how poorly Waimanu was supported as a penguin- 
> "Waimanu is closer to penguins than to any other bird group in the 
> following combination of characters: some thoracic vertebrae are not 
> heterocoelous; synsacrum has 11-12 ankylozed vertebrae; hypotarsal crests 
> and grooves of the tarsometatarsus are not well-developed (but medial 
> hypotarsal crest is distinct)."
> Those look like three plesiomorphic states to me.

This may have more to do with the size of the matrix -- 148 characters --  
than with the fossil.