Author: Chris Nedin ( Title: All About _Archaeopteryx_ Upda

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====================================================================== Author: Chris Nedin ( Title: All About _Archaeopteryx_ Update: 6/28/94 ====================================================================== Contents Introduction Archaeopteryx specimens Archaeopteryx features Archaeopteryx's avian features Archaeopteryx's reptile features Cranial features of Archaeopteryx Protoavis Conclusions References Introduction _Archaeopteryx lithographica_ ("ancient wing from the printing stone") Named after the limestone in which it was discovered. The stone is a smooth, fine grained limestone which was used in printing. Quarried from in and around the Solnhofen area of Germany. Formed on the bottom of a hypersaline lagoon in the Cretaceous. There have been 7 specimens of _Archaeopteryx_ found (6 actual specimens and one feather). These finds are documented chronologically (by description) below. 1) The Feather Found in 1860 near Solnhofen and a revelation when it was described by H. v Meyer in 1861. The surprise was not the age of the fossil, since several ornithopod dinosaur footprints erroneously ascribed to birds were known from the Triassic, but the detail that was preserved. 2) The London Specimen Found in 1861, near Langenaltheim. Probably the best known (together with the Berlin specimen). Its discovery was announced by H. v Mayer in 1861 and the specimen was subsequently bought by the Richard Owen for the British Museum of Natural History in London. It cost 700 UK Pounds - a small fortune in those times, but for that price Owen also received a number of other fossils from Solnhofen. The specimen was sold by amateur collector and local doctor Carl Haberlein. Owen described the specimen in 1863. He saw at once that it was an important find and recognised that it represented a transitionary form - but not in the 'Darwin' sense. Owen was a staunch 'evolutionist', however he did not believe in Darwins model of evolution. Interestingly Huxley, who *was* a staunch 'Darwinist' failed to recognise the true import of the fossil and mearly remarked on it as a "reptile-like bird". It wasn't until close comparisons were made with the dinosaur _Compsognathus_ that Archae's true worth was realised. 3) The Berlin Specimen Found in 1877 near Blumenberg. This was a better specimen that the London specimen, principally because it had a complete head, albeit badly crushed, and was snapped up by the Berlin museum. It was sold to them by Carl Haberlein's son (talk about keeping it in the family!). It was described by W. Dames in 1884. 4) The Maxburg Specimen Found in 1958 near Langenaltheim (same as London Specimen). This specimen is of the torso only and as of 1990 was the only specimen to still be in private hands [note: I recall a specimen going on sale a year or two ago, it may well have been this specimen - cn]. The specimen was described by P. Wellnhofer in 1959. 5) The Haarlem or Teyler Specimen This specimen was actually found near Reidenburg in 1855, 5 years *before* the feather! It lay in a museum after being classified as _Pterodactylus crassipes_ by H. v Meyer in 1875. A re-examination of the fossil in 1970 by Ostrom revealed feathers and its true identity. 6) The Eichstatt Specimen Found near Workerszell in 1951, it was described by P. Wellnhofer in 1974. This is the smallest of all the specimens, being some 2/3 the size of the others. It also differs in other aspects such as the tooth structure and the poorly ossified sholder bones. It has been suggested that this is a separate genus, however the differences can also be ascribed to the possible juvenile stage of the animal and/or a different feeding niche. However, this specimen has the best preserved head and from which the litany of Archae's reptilian cranial features were described. At the moment it still resides within _A. lithographica_. 7) The Solnhofen Specimen Found in the 1960's near Eichstatt by a Turkish worker. First identified as _Compsognathus_, but further examination showed that the arms were too long for the body size and preparation revealed feather traces. Described by P. Wellnhofer in 1988 _Archaeopteryx_ features Much has been made in pseudoscientific circles about the position of Archae with the evolutionary scheme of things. The usual 'arguement' (and here I use the term in it's loosest possible sense) put forward is that Archae cannot be a transitionary fossil between birds and dinosaurs because it is a bird. This simplistic line belies the fact that, whilst Archae is indeed classified as a bird, it has been done so on the strength of 4 characters - 2 of which are not unique to birds. This classification ignores the fact that Archae has some15 characters which *are* unique, unique in that they are *not* possessed by birds. Archae's avian affinities are allowable on the strength of the following 4 characters: Archae's avian features: 1) Feathers Feathers are *the* diagnostic feature of birds. This is the main criterion for classifying Archae as a bird, as no other animal has feathers. The possession of feathers is a characteristic of birds, so strike one up for the birds. 2) Opposable hallux (big toe) This also is a character of birds and not dinosaurs. Although opposable big toes are found in other groups, they are not, as far as I am aware, found in dinosaurs. So strike another for the birds 3) Furcula (wishbone) formed of two clavicals fused together in the midline. Now we start getting on shaky ground. It used to be though that the possession of a furcula distinguished birds from dinosaurs. Indeed, up until recently even clavicles were few and far between in even non-avian theropod dinosaurs (the suggested closest group to the birds and from which the birds evolved - see Ostrom 1976). However, it has been found that theropod dinosaurs did indeed have clavicles (e.g. Bryant & Russell 1993) and they have been found in several species, e.g.: _Segisaurus_ _Velociraptor_ _Euparkeria_ _Ornithosuchus_ _Saltoposuchus_ _Ticinosuchus_ etc. It has been found that the clavicles are often small and poorly ossified. This is no surprise, since they are of little evolutionary advantage to your average theropod dinosaur. However, birds too show this variation in ossification, especially amongst the carniates and so the apparent absence of clavicles in some theropod dinosaurs may well be due to poor ossification rather than true absence. However, furculas *have* been found in some non-avian theropod dinosaurs, namely the Oviraptorosauria (Barsbold et al 1990, Bryant & Russell 1993). these include _Oviraptor_ and _Ingenia_. Thus furculas do *not* appear to be diagnostic to birds and certain members of the suggested closest group to the birds now appear to possess furculas so it is a neutral character A commonly cited critisism of this is that most of the non-avian theropod dinosaurs listed here post-date Archae. However, none of these is claimed as the ancester anyway. The presence of clavicles shows that this character is a feature of theropod dinosaurs and thus was probably present in early theropods (indeed _Euparkeria_ is a Triassic form). 4) Pubis elongate and directed backward This is a feature of birds, but it is also a feature of some theropod dinosaurs so is not diagnostic of birds - another neutral character Archae reptile features: 5) Premaxilla and maxilla are not horncovered This is posh talk for 'does not have a bill' 6) Premaxilla and maxilla bear teeth Birds do not possess teeth. Teeth are expressed in the embryo, but are lost before the chick is hatched 7) Nasal opening far forward, seperated from the eye by a large preorbital fenestra This is typical of reptiles, but not of birds 8) Cerebral hemispheres elongate, slender and cerabellum is situated behind the midbrain and does not overlap it from behind or press down on it. This again is a reptilian feature. In birds the cerebral hemispheres are stout, cerabellum is so much enlarged that it spreads forwards over the midbrain and compresses it downwards Skull and brain of Archae is basically reptilian and has *NO* unambiguous avian features and is not "totally birdlike" (contrary to a certain creationists claims) 9) Center of cervical vertebrae have simple concave articular facets. This is the same as the archosaur pattern. In birds the vertebrae are different, they have a saddle-shaped surface. 10) Long bony tail with many free vertebrae up to tip (no pygostyle). Birds have a short tail and the caudal vertebrae are fused to give the pygostyle. 11) Trunk region vertebra are free. In birds the trunk vertebrae are always fused. 12) Ribs slender, without joints or uncinate processes and do not articulate with the sternum. Birds have stout ribs with uncinate processes (braces between them) and articulate with the sternum 13) Pelvic girdle and femur joint is archosaurian rather than avian. With the exception of the backward pointing pubis as mentioned above. Here Archae really shows its transitionary nature. Whilst the pelvic girdle as a whole is basically free and similar to archosaur girdles, the pubis points backward - a character shared with birds and some other bird-like theropod dinosaurs. 14) Sacrum occupies 6 vertebra. This is the same as in reptiles and especially ornithipod dinosaurs. The bird sacrum (the vertebrae developed for the attachment of pelvic girdle) covers between 11-23 vertebrae! 15) Metacarpals (hand) free (except 3rd metacarpal) , wrist hand joint flexable. This is as in reptiles. In birds the metacarpals are fused together and with the distal carpals in the carpo-metacarpus, wrist /hand fused. All modern birds have a carpo-metacarpus, all fossil birds have a carpo-metacarpus - except one (guess! clue: the answer contains the letters a.r.c.h.a.e.o.p.t.r.y.x. in that order) :-) 16) Bones not pneumatic. I.e. they do not have air-sacs. They do in birds. 17) Claws on 3 digits, No modern bird has claws. The juvenile Hoatzin and ostrich do have 2 claws but loose them as they grow. In the case of the Hoatzin it is thought that these claws alow the juvenile to climb. 18) The fibula is equal in length to the tibia in the leg This again is a typical character of reptiles. In birds the fibula is shortened and reduced. 19) Metatarsals ( foot bones) free. In birds these are fused to form the tars-metatarsus 20) Gastralia present. Gastralia are "ventral ribs", elements of dermal bone in the ventral wall of the abdomen. Typical of reptiles, they are absent in birds. 1 = present; * = present in some; x = absent Dinosaurs Archae Birds 1 x 1 1 2 x 1 1 3 * 1 1 4 * 1 1 5 x x 1 6 1 1 x 7 1 1 x 8 1 1 x 9 1 1 x 10 1 1 x 11 x x 1 12 1 1 x 13 1 1 x 14 6 6 11-23 15 1 1 x 16 x x 1 17 1 1 * 18 1 1 x 19 1 1 x 20 1 1 x It can be seen that Archae possesses many more characters which are present in dinosaurs and *not* in birds, than it does characters which are present in birds but not in dinosaurs. This is why Archae is a true transitionary species, because it shares some characters which are diagnostic of one group whilst still retaining characters diagnostic of its ancestral group. Anyone who claims that Archae is 100% bird is wrong. Anyone who claims that Archae's skeleton is even predominantly bird-like is wrong. Anyone who claims Archae has a "totally birdlike" skull is wrong. This latter point is made in reference to the claim by Duane Gish that the skull of Archae is "totally birdlike. This is false. To show this we need to consider the skull of Archae further. Cranial features of Archae As stated above, Duane Gish claims that the skull of Archae is "totally birdlike". This is false. Romer (1950 p. 261) describes Archae thus: "The skull, as far as can be seen, was rather birdlike. . . ". However, not only is this a far cry from "totally birdlike", but Romer was using the detailed reconstruction of the Berlin Specimen, by Heilmann (1926). Ostrom (1976 p. 131) has this to say on the Heilmann reconstruction: "Despite the details shown there [Heilmann's reconstruction of the skull - cn], the actual specimen does not permit such detailed and precise conclusions. It [the Berlin specimen's skull - cn] is badly crushed and the bones are extensively fracture, chipped and distorted - to the extent that very few cranial or mandibular sutures unmistakably indentifiable. Heilmann's reconstructions have been republished by many authors and subsequent interpretations and hypotheses based on it. Quite probably, some authors have been unaware of the inadequate basis of Heilmann's reconstruction, and understandably so unless they have had the opportunity to examine the specimen itself." And again on the same page: "Fortunately, the Eichstatt speciman now provides a comparative basis for evaluating and correcting past reconstructions of the Berlin skull." As mentioned above, the Eichstatt speciman was not described until 1974, therefore Romer's description was based on the Heilmann reconstruction. Using both specimens, Ostrom (1976 p. 132) delineated 9 characters on the skull of Archae which it shares with other theropod dinosaurs such as _Ornitholestes_, _Compsognathus_, _Velociraptor_ and perhaps _Saurornithoides_. These are: 1) A sharply tapered snout. 2) long elliptical external nares bounded almost exclusively above and below by the premaxilla (a bone at the front of the upper jaw). 3) A large triangular antorbital fossa which contains two small anterior openings and a large triangular posterior fossa.(these are holes in the skull, one in front of the eye -with two openings - the other behind the eye) 4 A slender, nearly vertical preobrital bar separating the antorbital fossa and the orbit. (there's that hole again! This means that there is a vertical bar of bone separating the hole in front of the eye with the eye itself) 5) A large circular orbit which contains a large scleotic ring.(the sclerotic ring is common to reptiles, birds and actinoptygian fish, but most fossil reptiles and all fossil birds have them. They are a series of ossified plates which circle the eye) 6) A thin, straight jugal bone. (this is the bone that runs under the eye - the cheek-bone, as it extends back towards your ear, to you) 7) A stout quadrate of maderate length which is inclined forward. (this is the bone in the upper jaw which forms part of the jaw articulation - with the articular - in reptiles, and Archae has a big one, um if you see what I mean! Incidentally - for those of you who are still with us, the quadrate is attached to the stapes in the upper jaw, and as we all know, the stapes is the bone which vibrate in the ear so that we can all hear. Thus the stapes and quadrate were attached in reptiles and it is not a great leap forward to have both the stapes and the quadrate in the ear as it is in mammals. This also shows that Gish's claim that in order for the bones to enter the ear in the transition from reptiles to mammals they would have had to gone through a stage whereby the 'mammal' would have deafened itself every time it opened its mouth is bullshit since the condition of stapes+quadrate articulating in the jaw joint *is found in fossil and extant reptiles*, but I digress. 8) A lower jaw which is unusually shallow and has a conspicuous bend behind the tooth row. 9) A long retroarticular process. (again a classic reptile jaw-joint feature) Heilmann described an external mandibular fenestra (a hole in the lower jaw) bordered below by the dentary bone - which is the condition in birds - rather than by the angular bone - as it is in reptiles. This would indicate that Archae has a lower jaw which contained both avian (said mandibular fenestra) and reptilian features (toothed lower jaw). This is all very well and dandy and is a feature which one would like to see in Archae. However, as Ostrom (1976 p. 132) point out: "Much as I would like to accept this interpretation, the highly fractured condition of the lower jaw bone (or bones) that border the supposed mandibular fenestra, either below or above, make it impossible to certify their identifications. in fact, the fractured upper margins of the supposed fenestra leave considerable doubtas to the very existance of a 'fenestra' - a doubt which has not been removed by the Eichstatt specimen." Thus, far from conspiring to present Archae in the best possible light, a very useful feature which would have aided in the description of Archae as a true transitionary fossil has in fact been show to be, in all probability, not true. So much for the evilutionist conspiracy! Another important feature of the skull of Archae is the occipital condyle and the foramen magnum. In Archae these are well above the dorsal end of the quadrate. As Ostrom (1976 p. 136) says: "This primative condition is characteristic of both pseudosuchians and theropods, in contrast to all later birds where the occipital condyle and foramen magnum are at the base of the skull, well below the level of the upper extremity of the quadrate. In this feature, _Archaeopteryx_ was far from avian." As can be seen, Archae's skull possesses no diagnostically avian features, let alone is "totally birdlike". The "totally birdlike" claim is without foundation. _Protoavis_ Some people like to claim that the finding of a fossil bird from the Triassic of Texas (_Protavis_), proves that Archae cannot be transitionary between dinosaurs and birds because _Protoavis_ predates Archae by 75 million years. This is, of course, errant nonsense, mainly because no-one is claiming that Archae is *the* transitionary species between dinosaurs and birds, mearly that Archae represents a grade of organisation which the proposed lineage went through to get from dinosaurs to birds. Archae is, I'm sorry to say, out on a limb, evolutionarily speaking. It represents a side branch, useful for comparative purposes, but not in the thick of things. So even if there were birds in the Triassic, that fact would not diminish Archae's importance as an indicator that 'yes, birds could have evolved from dinosaurs". However, notice the "if" in the previous sentence. There are major problems with _Protoavis_. On the Chatterjee (1991) interpretation, Ostrom (1991) has this to say: [abridged] The only published material from the fossil is a monograph in the Philosophical Transactions of the Royal Society of London. However, this only describes the head. This is badly crushed and all the pieces have been extracted from the matrix, rendering precise placement of the pieces open to question. The description is done from an avian viewpoint, with no counterview (ie is this a dinosaur?) used. The skull is so badly crushed that diagnostic features are not preserved. Therefore the published material does not support the view that this is a bird. Indeed a viewing of the fossil by Ostrom (in admittedly less than ideal surroundings) showed that the diagnostic features which could identify the fossil either way are badly crushed and it is doubtful wether any definative statement could be supported by the fossil. It may be a bird, it may not. Please note that this questioning of _Protoavis_ as a bird is no "it can't be a bird because it predates Archae" evilutionist backlash. As has been pointed out, even if it is a bird, it does not detract from the evolutionary importance of Archae. Conclusions _Archaeopteryx_ is a bird because it had feathers. However, it retaines many dinosaurian characters which are not found in birds, whilst having certain characters found in birds but not in dinosaurs. By virtue of this fact _Archaeopteryx_ represents a example of a group in transition. A representative which, although on the sidelines in the dinosaur to bird transition, an echo of the actual event, still allows a brief glimpse into the possible mechanism which brought about the evolution of the birds and by its very existance shows that such a transition is possible. Referencess Barsbold, R. et al 1990. Oviraptorosauria. In The Dinosauria, Weishampel, Dodson & Osmolska (eds) pp 249-258. Bryant, H.N. & Russell, A.P. (1993) The occurrence of clavicles within dinosauria: implications for the homology of the avian furcula and the utility of negative evidence. Journal of Vertebrate Paleontology, 13(2): 171-184. Chatterjee, S. (1991) Cranial anatony and relationships of a new Triassic bird from Texas. Phil. Trans. R. Soc. Lond. B. 332: 277-342 Heilmann, G. (1926) The Origin of Birds. 208pp. Witherby, London Ostrom, J. H. (1976) Archaeopteryx and the origin of birds. Biological Journal of the Linnean society, 8(2): 91-182. Ostrom, J.H. (1991) Bird in the Bush. Nature, 353: 212 Romer. A.S. (1950) Vertebrate Paleontology. p 261. University of Chicago Press, Chicago. Acknowledements This came about as the result of a series of discussions with Rich Trott, who was fighting the systematic misuse of Archae by His Gishness and others, and still managed to find the time to suggest improvements to this post


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