Talk:Protoavis

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[edit] Protoavis fossils

Chatterjee (1995) describes these Protoavis specimens in addition to the description of the skeletons referred to TTU P 9200 and TTU P 9201. They are:

(TTU P 9350-9355) six dorsal vertebrae (6-10 mm)

(TTU P 9356-9359) four caudal vertebrae (8-9 mm)

(TTU P 9360) coracoid(?) (14 mm)

(TTU P 9361) sternum(?) (25 mm)

(TTU P 9362) humerus (~80 mm)

(TTU P 9263) humerus

(TTU P 9364) partial mandible

(TTU P 9365) humerus

(TTU P 9370) femur (~58 mm)

(TTU P 9372) femur

(TTU P 9373) femur

(TTU P 9374) tibia

(TTU P 9375-9380) phalanges

femur (http://www.texasfinearts.com/Views/2006FieldNotes.htm)

Sources:

Chatterjee, S. 1995. The Triassic bird Protoavis. Archaeopteryx 13: 15-31.

http://www.texasfinearts.com/Views/2006FieldNotes.htm

Add details about the material referred to Protoavis. 72.194.116.63 14:04, 25 March 2007 (UTC)Vahe Demirjian 07.00 25 March 2007

[edit] Bird-like footprints from the Triassic of Argentina

Melchor et al. (2002) discovered footprints from the Late Triassic of Argentina they said were evidence for the existence of birds in the Triassic. They also concluded that earlier reports of supposed pre-Archaeopteryx bird footprints were actually attributable to non-avian dinosaurs. The discovery of avian footprints from the Late Triassic of Argentina will force paleontologists to revisit Protoavis and seriously consider that fossil to be truly avian. It's likely that fossil birds from the Late Triassic-Late Jurassic are to found in the future. Two countries that might yield pre-Archaeopteryx fossils of birds would be the People's Republic of China and Vietnam. A photo of the avian footprints from the Late Triassic from Argentina was taken from http://www.agiweb.org/geotimes/june02/WebExtra0627.html.

Sources:

MELCHOR, RICARDO N., SILVINA DE VALAIS & JORGE F. GENISE, 2002. Bird-like fossil footprints from the Late Triassic. Nature 417, 936 - 938 (2002).

"they said were evidence for the existence of birds in the Triassic" - no they don't say "evidence"; else they would have would have called their paper "avian" instead of "bird-like" (verbatim, they say "an unknown group of Late Triassic theropods having some avian characters" which is fair and square and good scientific practice). The inverted hallux as a (presumably) avian autapomorphy is adaptive in character (improved perching ability at the price of worse running ability - cursorial birds tend to loose the hallux entirely) and thus given the close relationships of birds and non-avian theropods and considering that some "typically avian" features (feathers, flight etc) are now known to be synapomorphies shared between Aves and other Maniraptora it is not inconceivable that these footprints are from a small perching non-avian reptile. (Indeed it seems due to the fact that there were several lineages of early birds, "avian autapomorphies" as opposed to "neornithine autapomorphies" are increasingly hard to point out).
Emu footprints usually cannot be distinguished from those of some dinosaurs except by age, which should serve as a warning. Besides, the locality Argentina is odd indeed. Given that Argentine deposits have been comparatively well worked over, one would expect that if there were anything diagnosably avian around from approximately before the Lecho Formation was deposited (Late Cretaceous - 70-65 mya!), it would have been found by now. The temporal gap between the Lecho and Santo Domingo formations is about twice of what it is between the Dockum Formation and the Solnhofen limestones, and there is no indication of a Gondwanan/American origin of the Aves at present. One footpront, or even 520 footprints per square meter, do not make a bird; the summary of all available evidence does. The paper is good and will go into the article though. Dysmorodrepanis 14:52, 5 October 2006 (UTC)

[edit] Abstract from Protoavis description (1991)

The abstract from Chatterjee (1991) reads:

The oldest known fossil bird from the Late Triassic (about 225 million years ago) Dockum Formation of Texas, provides insights into the anatomy, evolution and phylogenetic relationships of early birds. In life, this adult bird was about the size of a pheasant (Phasianus) counting its long bony tail. Many characters of the skull show that the Texas species is more closely related to other birds than to any known group of archosaurs. The skull is lightly built, pneumatized, with an enormous orbit and expanded temporal region. The teeth are restricted to the tip of the jaws, the posterior teeth having been lost. The temporal region is modified from the diapsid condition, as in modern birds, where the orbit is confluent with the upper and lower temporal openings because of the breakdown of the temporal arcades. The relatively large brain size and the modification of the brain architecture in avian fashion show neurosensory specializations that may be associated with balance, coordination, flight, agility and high metabolic activity. The new species had binocular vision, which suggests that it was a visually oriented predator. Auditory acuity may be associated with vocal behaviour. The quadrate was streptostylic and the whole upper jaw was moved prokinetically as in modern birds. Among current hypotheses for the relationships of birds among archosaurs, both theropod and crocodilian hypotheses have been supported by shared apomorphies. Some of the avian features in the crocodilian skull may have been acquired convergently because of homoplasy. Conversely, the highly akinetic skull and monimostylic quadrate along with primitive brain architecture in early crocodylomorphs negate its close phyletic relationships with birds. Within archosaurs, the theropods are closest to birds, but just what taxon is the sister group among theropods is uncertain at this time. Numerical cladistic analysis of 30 cranial characters generated a hypothesis of the phylogenetic pattern of early avian evolution. By using theropods and sphenosuchids as comparative outgroups and root for the tree, the analysis confirms the monophyly of the class Aves. Archaeopteryx is the most primitive taxon and is sister group to all other birds. Archaeopteryx, Avimimus and the Texas bird are successively closer to the remaining avian taxa or Ornithurae. Hesperornis, Ichthyornis and Gobipteryx are the Cretaceous representatives of the Ornithurae. The Triassic bird extends the known avian record back at least 75 million years and documents an early stage in the evolution of modern birds. The avian skull evolved in response to two functional requirements: efficient feeding mechanism, leading to the development of cranial kinesis, and neurosensory specializations leading to the enlargement of the braincase and orbit. Cranial kinesis, braincase inflation and otic specialization greatly modified the architecture of early avian skulls from the theropod condition. Phylogenetic analysis suggests that theropods shared a common ancestry with birds, but it is indeterminate from the fossil record whether or not the immediate common ancestor itself was a theropod.

Is the information in this article based on real evidence or not?

Chatterjee, S. 1991. Cranial anatomy and relationships of a new Triassic bird from Texas. Philosophical Transactions of the Royal Society of London, B 332: 277-342.

The authors believe it to be real. Most others believe that many of the elements described come from various types of animals. see the EvoWiki article on Protoavis, cited above.Dinoguy2 04:34, 14 September 2006 (UTC)
I can only advise anyone pondering this question to acquire a copy of the Rise of Birds and then start wondering why there is not a single photograph in it of the bones and why all drawings are interpretative instead of accurate ;o).--MWAK 11:22, 1 November 2006 (UTC)

[edit] Phylogenetic implications

If Protoavis is really closer to the pygostyles than to Archaeopteryx, then Archaeopteryx would be considered a parallel lineage of the Aves. Mayr et. al. (2005) showed Archaeopteryx to a hyper-extendible second toe, a feature previously seen only in deinonychosaurs. This means that Archaeopteryx is closer to the deinonychosaurs than to pygostyles, because the hyper-extendible second toe is a synapomorphy linking Archaeopteryx with the deinonychosaurs.

Mayr, G., B. Pohl & D.S. Peters (2005). A well-preserved Archaeopteryx specimen with theropod features. Science 310 (5753): 1483-1486.

Unfortunately, this is not widely accepted just yet and will probably take a long, long time to become so. If Archie is closer to deinonychosaurs than pygostylians, a number of classification changes would need to take place. Dromaeosauridae would probably be sunk into Archaeopterygidae, deinonhychosaurs we be considered true avian birds under almost all existing definitions of Aves, etc.Dinoguy2 02:18, 4 October 2006 (UTC)
Most definitions of Aves or Avialae use Archaeopteryx as a defining species. The position of Protoavis is simply irrelevant.--MWAK 11:06, 1 November 2006 (UTC)

[edit] New papers on Protoavis

Recent papers on Protoavis are as follows:

Martin, L.D. 2004. A basal archosaurian origin for birds. Acta Zoologica Sinica 50(6): 978-990.

Lehman, T. and Chatterjee, S. 2005. Depositional setting and vertebrate biostratigraphy of the Triassic Dockum Group of Texas. Journal of Earth System Science, 114: 325-351.

There have been no new papers concerning Protoavis since Lehman & Chatterjee (2005). 72.194.116.63 01:26, 5 March 2007 (UTC) Vahe Demirjian 17.24 4 March 2007

[edit] Possible explanation for the disarticulation of the Protoavis remains

If the material referred to Protoavis was found disartculated, the reason for the unusual circumstances of discovery is probably because the bones were originally articulated, but then were washed away by a huge river stream.

The only evidence to suggest that Protoavis is chimeric is the coelophysoid affinity of 2 ankle bones and a femur referred to Protoavis, which belong to a juvenile coelophysid, possibly Coelophysis (Nesbitt et. al., 2005), the pterosauromorphan affinity of an ischium, 4 tarsals, 4 metatarsals, tibia, and fibula referred to Protoavis, which belong to a pterosauromorph (Atanassov, 2001, 2002), and the drepanosaurid affinity of some neck vertebrae assigned to Protoavis (Renesto, 2000). However, this evidence can do little or nothing to prove that Protoavis is a chimera.

Atanassov, 2001. Two new archosauromorphs from the Late Triassic of Texas. Journal of Vertebrate Paleontology. 21(3) 30A.

Atanassov, 2002. Unpublished thesis. Texas Tech University.

Nesbitt, Irmis and Parker, 2005. Critical review of the Late Triassic dinosaur record, part 3: Saurischians of North America. JVP 25(3) 96A. 72.194.116.63 15:28, 25 March 2007 (UTC) Vahe Demirjian 08.27 25 March 2007

It is not up to anyone to prove "Protoavis" is a chimera. The fossils were disarticulated when discovered, and assembled from multiple locations. "Further material assigned to the taxon has been recovered in isolation with no apparent spatial relationships to each other, and more or less has been referred to Protoavis on a whim." [1] And the Atanassov paper you mention indicates "Protoavis" is indeed chimeric, as some of the fossils referred to "Protoavis" have been identified by Atanassov as being from an undescribed pterosauromorph from the Late Triassic. Also, please sign your posts by typing four tildes (~~~~). Firsfron of Ronchester 01:17, 13 October 2006 (UTC)

[edit] The bird evolution revolution

Kurochkin (2006) showed that the characters that birds share with theropod dinosaurs are convergent with those of theropods. He concluded that the clade Sauriurae (Archaeornithes + Enantiornithes) shares a number of characters with theropods, suggesting that sauriurines evolved from theropods in the Late Jurassic, and that the clade Ornithurae and Protoavis (which is placed in its own subclass, Praeornithurae) evolved from an archosaur ancestor in the Late Triassic. I think that this paper is important because it completely ends the debate on the origins of birds by disproving that modern birds evolved within the Coelurosauria. The argument that the ornithurines evolved from an archosaur ancestor is based on how the fingers of living birds are different from those of tetanuran dinosaurs. Kurochkin (1995, 2006) accepts Protoavis as an ancestral bird that evolved into the ornithurines.

Add this paper to the section References.

The abstract of this paper reads:

The hypothesis of the direct origin of birds from theropod dinosaurs has recently become widespread. Direct sisterly relationships between theropods and birds were assumed in the basis of random and formal synapomorphies, such as the number of caudal vertebrae, relative length of the humerus, and flattening of the dorsal margin of the pubis. In essence, this hypothesis is supported by the characters of theropods and birds, such as the presence of feathering, furcula, uncinate processes of ribs, pygostyle, double-condyled dorsal joint of the quadrate, and posteriorly turned pubis, which are recognized as homologies. Until recently, these characters have been regarded as avian apomorphies; however, they are presently known in various coelurosaurian groups. At the same time, they occur in various combinations in the Dromaeosauridae, Troodontidae, Oviraptoridae, Therizinosauridae, and Tyrannosauridae. None of the theropod groups possesses the entire set of these characters. This suggests that theropods and birds acquired them in parallel. Theropod dinosaurs and Sauriurae (Archaeornithes and Enantiornithes) show a number of important system synapomorphies, which indicate that they are closely related. Ornithurine birds lack such synapomorphies; however, their monophyly is supported by a large number of diagnostic characters. The hypothesis of independent origin of Sauriurae and Ornithurae is substantiated; the former are considered to have evolved from theropods in the Jurassic, while the latter deviated from a basal archosauromorph group in the Late Triassic. The hypothesis that birds existed in the Early Mesozoic is supported by the findings of small avian footprints in the Upper Triassic and Lower Jurassic of different continents.

Kurochkin, E. N., 1995. Synopsis of Mesozoic birds and early evolution of Class Aves. Archaeopteryx. 13, 47-66.

Kurochkin, E. N., 2006, Parallel evolution of theropod dinosaurs and birds: Zoologicheskii Zhurnal, v. 85, n. 3, p. 283-297.

Alas, Kurochkin shows nothing of the kind: he merely makes unsubstantiated claims founded on nothing more than the supposed superiority of his insight. See http://dml.cmnh.org/2006Oct/msg00467.html.. A statement like: "None of the theropod groups possesses the entire set of these characters. This suggests that theropods and birds acquired them in parallel." suffices to show he has as yet failed to grasp modern methodology.--MWAK 11:01, 1 November 2006 (UTC)
And there is also the "theory" that GOD created the birds in the fifth day of creation. Bible is a very reliable source since it is so popular (all these commonfolk can't be wrong). My ignorant opinion is that the non-dinosaur origin of birds are a sign of pseudoscientific conservatism related to the popular view of dinosaurs being with slow metabolism, cold blooded, gargantuan lizzards. If this kind of opinion were to prevail over evidence we would still think that tyrannosaurus looked like godjila and iguanodon like a kangaroo or, even worse, a gigantic tuatara with a thumpnail in its face.--Draco ignoramus sophomoricus (talk) 08:47, 9 May 2008 (UTC)

[edit] EvoWiki

  • Fyi, EvoWiki is not a reliable source of information, as it is a wiki. Wickethewok 19:39, 14 January 2007 (UTC)

[edit] Addition of many references

72 has just added tons of references for this article. While I appreciate the need for references, this article is now 50% article, 50% references. I'd like to trim back the reference section a bit. Thoughts? Firsfron of Ronchester 22:36, 25 March 2007 (UTC)