[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: "Dinosaurs Died Within Hours After Asteroid Hit Earth..."
David Marjanovic wrote-
> > There was quite a diversity of
> > neornithines that survived (galliformes, anseriformes, charadriiformes,
> > cormorants, albatrosses, loons),
> Though... the Cretaceous record of albatrosses is limited to a _furcular
> fragment_, so I simply don't believe it; the cormorant remains are more
> convincing, but consist only of tarsometatarsi, and we don't know what a
> tarsometatarsus of a basal flying hesperornithiform -- like what
> *Potamornis* could well have been -- looked like.
Very poor argument. First of all, the specimens Hope (2002) describes are a
scapula and a femur. She lists three scapular synapomorphies to support
this, and six femoral ones (two of which are unique to the clade). Second,
hesperornithines aren't neognaths, so even basal volant forms will lack the
synapomorphies grouping carinates and higher clades together. Metatarsal
characters include hypotarsi with distinct crests and grooves (at least one
enclosed by bone posteriorly), and a forked distal vascular foramen with two
Third, we DO have what's interpreted as a basal flying hesperornithine
Late Campanian-Early Maastrichtian, Late Cretaceous
Nemegt Formation, Mongolia
Material- (PIN 4491-8) incomplete tarsometatarsus
partial mandible, cervical vertebra
Comments- Hesperornithiform characters include- inclined cross section of
tarsometatarsal shaft; high proximal position of second trochlea; proximal
position for facet of metatarsal I. Supposedly diagnostic characters are-
tarsometatarsus stout and short; metatarsal shaft transversely expanded.
The fact these bones are small and highly pneumatized suggests to Kurochin
this species was volant.
Reference- Kurochkin, 2000. Mesozoic birds of Mongolia and the former USSR.
in Benton et al., eds. The Age of Dinosaurs in Russia and Mongolia. 533-559.
As for the albatross, there's also Lonchodytes, which seems to be a