   #copyright

Archaeopteryx

2007 Schools Wikipedia Selection. Related subjects: Birds

          iArchaeopteryx

                         Fossil range: Late Jurassic

   A model of Archaeopteryx lithographica on display at the Oxford
   University Museum
   A model of Archaeopteryx lithographica
   on display at the Oxford University Museum
                      Scientific classification

   Kingdom: Animalia
   Phylum:  Chordata
   Class:   Aves
   Order:   Archaeopterygiformes
   Family:  Archaeopterygidae
            Huxley, 1871
   Genus:   Archaeopteryx
   Species: A. lithographica

                                Binomial name

   Archaeopteryx lithographica
   Meyer, 1861

                                  Synonyms

   see text

   Archaeopteryx (from Ancient Greek αρχαιος archaios meaning 'ancient'
   and πτερυξ pteryx meaning 'feather' or 'wing'; pronounced
   /ɑː(ɹ)kiːˈɒptəˌɹɪks/), from the late Jurassic Period ( Kimmeridgian
   stage, 155-150 million years ago) of what is now Germany, is the
   earliest and most primitive known avian. Archaeopteryx was similar in
   size and shape to a magpie, with broad, rounded wings and a long tail.
   Its feathers resembled those of modern birds but Archaeopteryx was
   rather different from any bird known today, in that it had jaws lined
   with sharp teeth, three 'fingers' ending in curved claws and a long
   bony tail. In 1862, the description of the first intact specimen of
   Archaeopteryx, just two years after Charles Darwin published The Origin
   of Species, set off a firestorm of debate about evolution and the role
   of transitional fossils that endures to this day.

Archaeopteryx and the origins of birds

   In the 1970s, John Ostrom argued that the birds evolved from theropod
   dinosaurs (see Dinosaur-bird connection). Archaeopteryx provides a
   critical piece of this argument, as it preserves a number of avian
   features (a wishbone, flight feathers, wings, a partially reversed
   first toe) and a number of dinosaur and theropod features (for
   instance, a long ascending process of the astragalus, interdental
   plates, an obturator process of the ischium, and long chevrons in the
   tail). In particular, Ostrom found that Archaeopteryx was remarkably
   similar to the theropod family Dromaeosauridae. Further research on
   dinosaurs from the Gobi Desert and China has since provided more
   evidence of a link between Archaeopteryx and the dinosaurs, such as
   Chinese feathered dinosaurs.

   Archaeopteryx is probably close to the ancestry of modern birds - it
   shows most of the features one would expect in an ancestral bird - but
   it may not be the direct ancestor of living birds, and it is arguable
   how much divergence was already present in the early birds at its time.

Plumage

   Archaeopteryx specimens were most notable for their well-developed
   remiges. These are markedly asymmetrical and show the structure of
   flight feathers of modern birds, with vanes given stability by a barb-
   barbule-barbicel arrangement. The tail feathers are less asymmetrical,
   again in line with the situation in modern birds, and also have firm
   vanes. The thumb did not bear a separately movable tuft of stiff
   feathers ( alula) yet.

   Body plumage is less well documented, and only properly researched in
   the well-preserved Berlin specimen. Thus, as more than one species
   seems to be involved, the following does not necessarily hold true for
   all of them. In the Berlin specimen, there are "trousers" of
   well-developed feathers on the legs; some of these feathers seem to
   have a basic contour feather structure but are somewhat decomposed
   (i.e., lack barbicels as in ratites: Christiansen & Bonde, 2004), but
   at least in part they are firm and thus capable of supporting flight
   (Longrich, 2006).

   There was a patch of pennaceous feathers running along the back which
   was quite similar to the contour feathers of the body plumage of modern
   birds in being symmetrical and firm (though not as stiff as the
   flight-related feathers). Apart from that, the feather traces in the
   Berlin specimen are limited to a sort of "proto- down" not dissimilar
   to that found in the dinosaur Sinosauropteryx, being decomposed and
   fluffy, and possibly even appeared more like fur than like feathers in
   life (though not in their microscopic structure). These occur on the
   remainder of the body, as far as such structures are both preserved and
   not obliterated by preparation, and the lower neck (Christiansen &
   Bonde, 2004).

   On the other hand, there is no indication of feathering on the upper
   neck and head; while these may conceivably have been nude as in many
   closely related feathered dinosaurs for which good specimens are
   available, this may still be an artifact of preservation: it appears
   that most Archaeopteryx specimens became embedded in anoxic sediment
   after drifting some time on their back in the sea - the head and neck
   and the tail are generally bent downwards which suggests that the
   specimens had just started to rot when they were embedded, with tendons
   and muscle relaxing so that the characteristic shape of the fossil
   specimens was achieved. This would mean that the skin was already
   softened and loose (further evidence is provided by the fact that in
   some specimens, the flight feathers were starting to detach at the
   point of embedding in the sediment), and in specimens moving along the
   ground in shallow water, this would cause the head and upper neck, but
   not the more firmly attached tail feathers to slough off (Elżanowski,
   2002).

   It must be mentioned that the feather, the initial specimen described,
   does not agree too well with the flight-related feathers of
   Archaeopteryx. It certainly is a remix of a contemporary species, but
   its size and proportions indicate that it probably belongs to an as of
   yet undiscovered species of primitive bird or possibly bird-like
   dinosaur. As the feather was the original type specimen, this has
   created quite some nomenclatorial confusion.

Flight ability

   The flight feathers of Archaeopteryx were highly asymmetrical, as in
   the wings of modern birds, and the tail feathers are rather broad. This
   implies that the wings and tail were used for lift generation, but it
   is unclear whether Archaeopteryx was simply a glider, or capable of
   flapping flight. The lack of a bony breastbone suggests that
   Archaeopteryx was not a very strong flier, but flight muscles might
   have attached to the thick, boomerang-shaped wishbone, the platelike
   coracoids, or perhaps to a cartilagenous sternum. The sideways
   orientation of the glenoid (shoulder) joint between scapula, coracoid
   and humerus - instead of the dorsally angled arrangement found in
   modern birds - suggests that Archaeopteryx was unable to lift its wings
   above its back, a requirement for the upstroke found in modern flapping
   flight. Thus, it seems likely that Archaeopteryx was indeed unable to
   use flapping flight as modern birds do, but it may well have utilized a
   downstroke-only flap-assisted gliding technique (Senter, 2006).

   Archaeopteryx wings were relatively large, which would have resulted in
   a low stall speed and reduced turning radius. The short and rounded
   shape of the wings would have increased drag, but could also have
   improved Archaeopteryx' ability to fly through cluttered environments
   such as trees and brush (similar wing shapes are seen in birds which
   fly through trees and brush, such as crows and pheasants). The presence
   of "hind wings", asymmetrical flight feathers stemming from the legs
   similar to those seen in dromaeosaurids such as Microraptor, would also
   have added to the aerial mobility of Archaeopteryx. The first detailed
   study of the hind wings by Longrich (2006) suggested that the
   structures formed up to 12% of the total airfoil. Considering that it
   is not certain to what extent such feathers capable of supporting
   flight were present on the legs, this would have reduced stall speed by
   up to 6% and turning radius by up to 12%, in addition to the stall and
   turning radius reduction provided by the primary wing and tail
   feathers.

   In 2004, scientists analyzing a detailed CT scan of Archaeopteryx's
   braincase, concluded that its brain was significantly larger than that
   of most dinosaurs, indicating that it possessed the brain size
   necessary for flying. The overall brain anatomy was reconstructed using
   the scan. The reconstruction showed that the regions associated with
   vision took up nearly one-third of the brain. Other well-developed
   areas involved hearing and muscle coordination (Winter, 2004). The
   skull scan also revealed the structure of the inner ear. The structure
   more closely resembles that of modern birds than the inner ear of
   reptiles. These characteristics taken together suggest that
   Archaeopteryx had the keen sense of hearing, balance, spatial
   perception and coordination needed to fly (Alnso et al., 2004).

   Archaeopteryx continues to play an important part in scientific debates
   about the origin and evolution of birds. Some scientists see
   Archaeopteryx as a semi-arboreal climbing animal, following the idea
   that birds evolved from tree-dwelling gliders (the "trees down"
   hypothesis for the evolution of flight proposed by O.C. Marsh). Other
   scientists see Archaeopteryx as running quickly along the ground,
   supporting the idea that birds evolved flight by running (the "ground
   up" hypothesis proposed by Samuel Wendell Williston). Still others
   suggest that Archaeopteryx might have been at home both in the trees
   and on the ground, like modern crows, and this latter view is what
   today is considered best-supported by morphological characters.
   Altogether, it appears that it was a species which was neither
   particularly specialized for running on the ground, nor for perching.
   Considering the current knowledge of flight-related morphology, a
   scenario as outlined by Elżanowski (2002), namely that Archaeopteryx
   used its wings mainly to escape predators by glides punctuated with
   shallow downstrokes to reach successively higher perches, and
   alternatively to cover longer distances by (mainly) gliding down from
   cliffs or treetops, appears quite reasonable.

   Given that it is now well established that several lineages of
   theropods evolved feathers and flight independently, the question of
   how precisely the ancestors of Archaeopteryx became able to fly has
   lost dramatically in importance for the time being. Since it is quite
   likely that this species belongs to a lineage of birds unrelated to the
   Neornithes (the Jurassic ancestor of which remains unknown), how
   exactly flying ability was gained in Archaeopteryx may be a moot point,
   having little bearing on how this happened in the ancestors of modern
   birds.

Taxonomy

   The relationships of the specimens are problematic. Most specimens have
   been given their own species at one point or another. The Berlin
   specimen has been referred to Archaeornis siemensii, the Eichstätt
   specimen to Jurapteryx recurva, the Munich specimen to Archaeopteryx
   bavarica and the Solnhofen specimen was referred to Wellnhoferia
   grandis.

   Recently, it has been argued that all the specimens belong to the same
   species ( New Scientist, 17 April 2004, p.17). However, significant
   differences exist among the specimens. In particular, the Munich,
   Eichstätt, Solnhofen and Thermopolis specimens differ from the London,
   Berlin, and Haarlem specimens in being smaller or much larger, having
   different finger proportions, having more slender snouts, lined with
   forward-pointing teeth and possible presence of a sternum. These
   differences are as large as or larger than the differences seen today
   between adults of different bird species. However, it is also possible
   that these differences could be explained by different ages of the
   living birds.

Fossils

   Over the years, ten specimens of Archaeopteryx have been found. All of
   the fossils come from the limestone deposits near Solnhofen, Germany.
    1. The feather: Discovered in 1860 near Solnhofen, Germany, and
       described in 1861 by Hermann von Meyer. Currently located at the
       Humbolt Museum für Naturkunde in Berlin. This is generally referred
       to Archaeopteryx and was the initial holotype, but whether it
       actually is a feather of this species or another, as yet
       undiscovered, proto-bird is unknown. There are some indications it
       is indeed not from the same animal as most of the skeletons (the
       "typical" A. lithographica) (Griffiths, 1996).
       The London Archaeopteryx, 1863, detail, note the feathers
       Enlarge
       The London Archaeopteryx, 1863, detail, note the feathers
    2. London Specimen (BMNH 37001): Discovered in 1861 near
       Langenaltheim, Germany and described in 1863 by Richard Owen as
       Archaeopteryx macrura, assuming it did not belong to the same
       species as the feather. Currently located at the British Museum of
       Natural History in London, it is missing its head.
       The Berlin Archaeopteryx, 1881
       Enlarge
       The Berlin Archaeopteryx, 1881
       In a subsequent edition of his Origin of Species (chap. 10,
       pp.335-336), Charles Darwin acclaimed Owen's discovery as linking
       lizard-like reptiles with modern birds.
    3. Berlin Specimen (HMN 1880): Discovered in 1876 or 1877 on the
       Blumenberg near Eichstätt, Germany, by Jakob Niemeyer. He exchanged
       this precious fossil for a cow, with Johann Dörr. It was described
       in 1884 by Wilhelm Dames. Currently Located at the Humbolt Museum
       für Naturkunde, it is the best specimen, and the first with a
       complete head. Once classified as a new species, A. siemensii, but
       a recent evaluation supports the A. siemensii species definition
       [Elzanowski, 2002].
    4. Maxberg Specimen (S5): Discovered in 1956 or 1958 near
       Langenaltheim and described in 1959 by Heller. Currently missing,
       though it was once exhibited at the Maxberg Museum in Solnhofen. It
       belonged to Eduard Opitsch, who loaned it to the museum. After his
       death in 1991, the specimen was discovered to be missing and may
       have been stolen or sold. It is composed of a torso.
    5. Haarlem Specimen (TM 6428, also known as the Teyler Specimen):
       Discovered in 1855 near Riedenburg, Germany and described as a
       Pterodactylus crassipes in 1875 by von Meyer, it was reclassified
       in 1970 by John Ostrom. Currently located at the Teyler Museum in
       Haarlem, the Netherlands. It was the very first specimen, despite
       the classification error.
    6. Eichstätt Specimen (JM 2257): Discovered in 1951 or 1955 near
       Workerszell, Germany and described by Peter Wellnhofer in 1974.
       Currently located at the Jura Museum in Eichstätt, Germany. It is
       the smallest specimen and has the second best head. Possibly a
       separate genus, Jurapteryx recurva or species A. recurva.
    7. Solnhofen Specimen (BSP 1999): Discovered in the 1960s near
       Eichstätt, Germany and described in 1988 by Wellnhofer. Currently
       located at the Bürgermeister-Müller-Museum in Solnhofen. It was
       originally classified as a Compsognathus by an amateur collector.
       It is the largest specimen known and may belong to a separate genus
       and species, Wellnhoferia grandis.
    8. Munich Specimen (S6, formerly known as the Solnhofen-Aktien-Verein
       Specimen):
       The Munich Specimen
       Enlarge
       The Munich Specimen
       Discovered in 1991 near Langenaltheim and described in 1993 by
       Wellnhofer. Currently located at the Paläontologische Museum
       München in Munich. What was initially believed to be a bony sternum
       turned out to be part of the coracoid (Wellnhofer & Tischlinger,
       2004), but a cartilainous sternum may have been present. May be a
       new species, A. bavarica.
    9. Bürgermeister-Müller Specimen: A ninth, fragmentary specimen, was
       discovered in 1997. A further fragmentary fossil was found in 2004.
       It is kept at the Bürgermeister-Müller Museum.
   10. Thermopolis Specimen Discovered in Germany. Long in a private
       collection, described in 2005 by Mayr, Pohl, and Peters. Donated to
       the Wyoming Dinosaur Centre in Thermopolis, Wyoming, it has the
       best-preserved head and feet. The "Thermopolis" specimen, was
       described in the December 2, 2005 Science journal article as "A
       well-preserved Archaeopteryx specimen with theropod features",
       shows that the Archaeopteryx lacked a reversed toe—a universal
       feature of birds—limiting its ability to perch in trees and
       implying a terrestrial lifestyle. This has been interpreted as
       evidence of theropod ancestry. The specimen also has a
       hyperextendible second toe. "Until now, the feature was thought to
       belong only to the species' close relatives, the deinonychosaurs."

Synonyms

   The synonymy of A. lithographica is extremely confused. Dozens of names
   have been published for the handful of specimens, most of which are
   simply spelling errors (lapsus). Originally, the name A. lithographica
   only referred to the single feather described by von Meyer. Swinton
   (1960) proposed that the name Archaeopteryx lithographica be officially
   transferred from the feather to the London specimen. The ICZN did
   suppress the plethora of alternative names initially proposed for the
   first skeleton specimens (ICZN, 1961), which mainly resulted from the
   acrimonious dispute between von Meyer and his opponent Johann Andreas
   Wagner (whose Griphosaurus - "enigmatic lizard" - was a vitriolic sneer
   at von Meyer's Archaeopteryx). In addition, descriptions of
   Archaeopteryx fossils as pterosaurs before their true nature was
   realized were also suppressed (ICZN, 1977).

   If two names are given, the first denotes the original describer of the
   "species", the second the author on whom the given name combination is
   based. As always in zoological nomenclature, putting an author's name
   in parentheses denotes that the taxon was originally described in a
   different genus.
     * Pterodactylus crassipes Meyer, 1857 [suppressed in favour of A.
       lithographica 1977 per ICZN Opinion 1070]
     * Rhamphorhynchus crassipes (Meyer, 1857) (as Pterodactylus
       (Rhamphorhynchus) crassipes) [suppressed in favour of A.
       lithographica 1977 per ICZN Opinion 1070]
     * Archaeopteryx lithographica Meyer, 1861 [nomen conservandum]
     * Scaphognathus crassipes (Meyer, 1857) Wagner, 1861 [suppressed in
       favour of A. lithographica 1977 per ICZN Opinion 1070]
     * Archaeopterix lithographica Anon., 1861 [lapsus]
     * Griphosaurus problematicus Wagner, 1861 [nomen oblitum 1961 per
       ICZN Opinion 607]
     * Griphornis longicaudatus Woodward, 1862 [nomen oblitum 1961 per
       ICZN Opinion 607]
     * Griphosaurus longicaudatum (Woodward, 1862) [lapsus]
     * Griphosaurus longicaudatus (Owen, 1862) [nomen oblitum 1961 per
       ICZN Opinion 607]
     * Archaeopteryx macrura Owen, 1862 [nomen oblitum 1961 per ICZN
       Opinion 607]
     * Archaeopterix macrura Owen, 1862 [lapsus]
     * Archaeopterix macrurus Egerton, 1862 [lapsus]
     * Archeopteryx macrurus Owen, 1863 [unjustified emendation]
     * Archaeopteryx macroura Vogt, 1879 [lapsus]
     * Archaeopteryx siemensii Dames, 1897
     * Archaeopteryx siemensi Dames, 1897 [lapsus]
     * Archaeornis siemensii (Dames, 1897) Petronievics, 1917
     * Archaeopteryx oweni Petronievics, 1917 [nomen oblitum 1961 per ICZN
       Opinion 607]
     * Gryphornis longicaudatus Lambrecht, 1933 [lapsus]
     * Gryphosaurus problematicus Lambrecht, 1933 [lapsus]
     * Archaeopteryx macrourus Owen, 1862 fide Lambrecht, 1933 [lapsus]
     * Archaeornis siemensi (Dames, 1897) fide Lambrecht, 1933? [lapsus]
     * Archeopteryx macrura Ostrom, 1970 [lapsus]
     * Archaeopteryx crassipes (Meyer, 1857) Ostrom, 1972 [suppressed in
       favour of A. lithographica 1977 per ICZN Opinion 1070]
     * Archaeopterix lithographica di Gregorio, 1984 [lapsus]
     * Archaeopteryx recurva Howgate, 1984
     * Jurapteryx recurva (Howgate, 1984) Howgate, 1985
     * Archaeopteryx bavarica Wellnhofer, 1993
     * Wellnhoferia grandis Elżanowski, 2001

   The last 4 taxa may be valid genera and species.

   "Archaeopteryx" vicensensis (Anon. fide Lambrecht, 1933) is a nomen
   nudum for what appears to be an undescribed pterosaur.

   Retrieved from " http://en.wikipedia.org/wiki/Archaeopteryx"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
