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Archaeorhynchus, new toothless beaked Liaoning ornithurine
From: Ben Creisler firstname.lastname@example.org
In case this paper has not been mentioned yet:
Zhou, Z. & Zhang, F. (2006). A beaked basal ornithurine
bird (Aves, Ornithurae) from the Lower Cretaceous of
China. ?Zoologica Scripta, 35, 363?373.
We report here one of the earliest known beaked
ornithurine birds from the Lower Cretaceous deposits in
Liaoning, northeast China. The new basal ornithurine,
Archaeorhynchus spathula gen. et sp. nov., has a
rhynchokinetic skull with toothless jaws. It also contains
over three dozen preserved gizzard stones, suggesting an
herbivorous diet. The distal end of the tibiotarsus is
unfused, enabling recognition of the astragalus with a
broad ascending process, generally similar to that of
Archaeopteryx. The new discovery sheds new light on our
understanding of the early radiation and diet
diversification of early birds in the Lower Cretaceous.
Aves Linnaeus, 1758
Ornithurae Haeckel, 1866 (sensu Gauthier & de Queiroz 2001)
Archaeorhynchus spathula gen. et sp. nov.
Holotype. IVPP (Institute of Vertebrate Palaeontology and
Palaeoanthropology, Beijing, China) collection number
V14287; subadult individual, nearly complete skeleton with
Etymology. The generic name is derived from the Greek
words archae and rhynch, meaning 'ancient beak'. The
specific epithet is derived from the Greek word spatha,
indicating the spathulate dentary.
Locality and horizon. Yixian, Liaoning Province, China;
Yixian Formation, Lower Cretaceous.
Diagnosis. A basal ornithurine bird distinguishable from
other Mesozoic ornithurines by the following combination
of characters: beak present on both upper and lower jaws;
premaxillae broad with slightly rounded tips; dentary
spathulate, decorated with elongated foramina or grooves
and a longitudinal ridge; sternum broad and strongly
notched caudally with a pair of long lateral trabeculae;
furcula with long and pointed acromion processes;
metatarsals II and IV subequal in length; hindlimb
shortened; ratio of femur to tibiotarsus 0.88; ratio of
forelimb (humerus + ulna + major metacarpal) to hindlimb
(femur + tibiotarsus + metatarsal III) about 1.35
Archaeorhynchus is a medium-sized bird, represented by a
partially articulated skull and nearly complete
postcranial bones mainly preserved in ventral view, in
association with feather impressions distributed on the
whole body. ....
As one of the most basal ornithurines, Archaeorhynchus has
retained several primitive features reminiscent of
enantiornithines or more basal birds. For instance, the
dentary is not strongly forked posteriorly as in
Apsaravis; the sternum is broad but not as elongated as in
Ambiortus (Kurochkin 1985) and Yanornis. The synsacrum
comprises only seven sacrals, similar to Confuciusornis
and the primitive enantiornithine Protopteryx, while both
Yanornis and Yixianornis have nine and Apsaravis has ten.
The fibula is long and nearly extends to the distal end of
the tibiotarsus while it is much more reduced in both
Yanornis and Yixianornis. The tarsometatarsus lacks a
distinctive vascular foramen, which is present in
Yixianornis, Yanornis and Apsaravis.
Archaeorhynchus is larger than most enantiornithines from
the Lower Cretaceous, but smaller than more basal birds
such as Archaeopteryx, Jeholornis, and Sapeornis. It has
greatly shortened legs compared to the wings, a feature
which bears some resemblance to the enantiornithine
Longipteryx and the largest Lower Cretaceous bird
Sapeornis, but is different from Archaeopteryx and other
ornithurines such as Yixianornis (Table 1). The shortening
of the leg in the basal ornithurine Archaeorhynchus
obviously represents a parallel evolution independent of
enantiornithines or more basal birds. Furthermore, the
most basal ornithurines Archaeorhynchus, Hongshanornis
(Zhou & Zhang 2005) and Liaoningornis (Hou et al. 1996)
are smaller than more derived ornithurines such as
Yanornis and Yixianornis, showing a trend of increasing
body size among ornithurines in the Cretaceous. In
contrast to the shorter legs in Archaeorhynchus,
Hongshanornis had significantly elongated legs (Table 1).
The habit and possible diet of Archaeorhynchus are
difficult to ascertain. Although the bill of
Archaeorhynchus has some ostensible similarities to that
of a duck, it lacks the characteristic latter's horny
lamellae on the interior of the beak near the cutting
edge. The bill of a bird is a key adaptation for feeding.
The tip of the moderately long and flat bill of the new
bird is not pointed; thus it was probably not suitable for
grabbing fish or insects. The predentary bone, which is
clearly present in Hongshanornis and in several other
presumably fish-eating ornithurine birds (Zhou & Zhang
2005), is absent in Archaeorhynchus. Since the specimen of
Archaeorhynchus contains over three dozen preserved
gizzard stones, it probably fed mainly on plants.
Also, I cnn't recall if this paper was mentioned yet.
Sorry for the duplication if so:
Food remains in Confuciusornis sanctus suggest a fish diet
J. Dalsätt, Z. Zhou, F. Zhang and P. G. P. Ericson Food
remains in Confuciusornis sanctus suggest a fish diet.
Naturwissenschaften advance online publication
Abstract: Despite hundreds of excellent fossils of
Confuciusornis, the most abundant group of birds in the
Early Cretaceous, ?Jehol Biota? in China, there is yet no
indication of the food choice of these birds. Here, we
describe fish remains preserved in the alimentary system
of a specimen of Confuciusornis sanctus from the Jiufotang
Formation. This find is about five million years younger
than all previously published confuciusornithid birds from
the Yixian Formation. Although it is unknown how common
fish was in the diet of Confuciusornis, the find does not
support previous hypotheses that it fed on plants or grain.