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Re: Mei example
Gregory Paul wrote-
> deinonychosaurians had avian features not found in Arch including loss of
> ectopterygoid process*, big sternal plates, ossified sternal ribs and
> uncinates, flattened central fingers, and longer primary feathers. If
> sickle-clawed dinosaurs were more derived and better fliers than earlier
Well, I agree with your general thoughts re: neoflightless derived
deinonychosaurs. Indeed, my last analysis had Archaeopteryx as a
deinonychosaur, so I'm certainly not opposed to radical eumaniraptoran
topologies. However, we have to take parsimony into account when deciding
if plesiomorphies in Archaeopteryx are reversals or symplesiomorphies. And
if the latter is true, did deinonychosaurs converge with birds or was
Archaeopteryx basal to a deinonychosaur-bird clade? Your characters
supposedly supporting placing Archaeopteryx outside Eumaniraptora (from DA)
are generally of two types.
1. Characters which evolved far down on the tree, which would cause much
homoplasy when considering the more birdlike characters of Archaeopteryx.
Included in this are- short cervical ribs; enlarged anterior dorsal
hypapophyses; ossified uncinate processes; ossified sternal ribs; four or
more costal facets on sternum; large ossified sterna; narrow supracetabular
shelf; well developed antitrochanter; anterior and greater trochanters more
confluent. These features first appear at the level of Tyrannoraptora,
Maniraptoriformes and/or Maniraptora. Thus, by saying Archaeopteryx's
primitive states aren't reversals, you are advocating placing it further
down on the tree than its numerous tyrannoraptoran, maniraptoriform and
maniraptoran characters would suggest.
2. Characters which are primitive in basal deinonychosaurs and/or birds,
suggesting they evolved convergently in the clades. Examples are- six or
more sacral vertebrae; pointed scapular tip; prominent acromion; flange on
manual phalanx II-1; more opisthopubic pelvis. For instance, basal troodont
ids (Mei, Sinovenator, Sinusonasus), microraptorians and some dromaeosaurids
(Adasaurus, Saurornitholestes, Variraptor) have only five sacrals. All
deinonychosaurs except Bambiraptor have blunt or expanded scapular tips, as
do Rahonavis and Confuciusornis. Sapeornis, Shenzhouraptor and
Confuciusornis all have small acromion processes. Sapeornis, Bambiraptor
and troodontids lack the flange on II-1. Rahonavis, Shenzhouraptor and
Unenlagia all have mesopubic pelvises.
This leaves comparatively few characters. Cervical semiheterocoely, which
isn't definitely absent from Archaeopteryx, and is often confused with
amphicoely (so its distribution is particularly suspect). A distally
expanded coracoid, which is absent from Sapeornis and Achillobator too. And
a few characters I haven't examined yet- no ectopterygoid process on
pterygoid; short quadrate; metacarpal III bowed more; calcaneum reduced.
> Why researchers continue to insist that
> Archaeopteryx and birds form a clade above deinonychosaurs,
> escapes me.
Because there are characters which support this, even after all the recent
birdy deinonychosaur and oviraptorosaur finds. You list 32 such characters
yourself on page 329 of your book, that support placing Archaeopteryx in
Avialae. Two agree with my list below, others have been disproven by recent
finds, I excluded others from my list due to different or ambiguous
distribution, and most (21) I haven't included yet. Note that in
comparison, you list only 20 characters supporting non-eumaniraptoran
Archaeopteryx. By your own list, Archaeopteryx should be avialan.
>From my dataset, if I constrain a standard topology and include only
unambiguous character distributons (characters are unquantified for
Archaeopteryx is closer to birds than oviraptorosaurs are because it has-
- elongate distal caudal vertebrae.
Lacking in short-tailed birds; also present in Ornitholestes and
- proximal caudal centra rectangular in transverse section.
Lacking in short-tailed birds; also present in Microvenator and
- reduced number of caudals with transverse processes.
Lacking in dromaeosaurids and Sinornithoides.
- distal caudal neural spines absent.
Also present in Sinosauropteryx, Alvarezsaurus and Nomingia.
- distal chevrons bifurcated anteriorly.
- subglenoid fossa on coracoid.
Lacking in Sinornithoides and Bambiraptor; also present in Neimongosaurus
- shortened metacarpal I.
Lacking in Deinonychus and confuciusornithids; also present in Scipionyx and
- supratrochanteric process on ilium.
Lacking in Bambiraptor and Sapeornis; also present in Chirostenotes,
Neimongosaurus and Erliansaurus.
Archaeopteryx is closer to birds than deinonychosaurs are because it has-
- maxilla-naris contact.
Lacking in Sapeornis; also present in most troodontids, Erlikosaurus,
Shuvuuia and Compsognathus.
- low number of maxillary teeth.
Lacking in Aberratiodontus; also present in Scipionyx (ontogenetic?).
- posterior jugal process not forked.
Also present in oviraptorosaurs and Huaxiagnathus.
- jugal process of palatine absent.
Also present in Shuvuuia, Erlikosaurus and Incisivosaurus.
- posterior dorsal centra with deep lateral fossae.
Lacking in Shenzhouraptor, Eocathayornis, Patagopteryx and Apsaravis; also
present in Patagonykus, Beipiaosaurus and Deinonychus.
- fewer caudal vertebrae.
Lacking in Shenzhouraptor and Jixiangornis; also present in NGMC 91,
Nomingia and Caudipteryx.
- even more elongate distal caudal vertebrae.
Lacking in short-tailed birds; also present in microraptorians.
- coracoid bent at smaller angle in posterior (edge on) view.
- coracoid proximodistally more elongate.
Lacking in Sapeornis; also present in Sinornithosaurus.
- metacarpal I even shorter
Lacking in confuciusornithids; also present in Microraptor and
Notice sometimes a basal deinonychosaur will have a character used to put
Archaeopteryx in Avialae. For instance, the elongate distal caudals of
birds and microraptorians. But since microraptorians are placed sister to
dromaeosaurids based on other evidence, it would be less parsimonious to
assume troodontids and dromaeosaurids both lost the character.
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database - http://students.washington.edu/eoraptor/Home.html