[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: A couple of questions
Ivan Kwan wrote-
OK, here's a few short questions for those in the know to answer:
1) Pterosaurs: Ornithodira (& thus the sister group to Dinosauria), or
Prolacertiformes? If they are prolacertiformes, would that exclude them
from the Archosauria?
If HP David Peters and Dr. Rupert Wild are correct, pterosaurs are derived
prolacertiforms, which makes them outside of the Archosauriformes, but in
the Archosauromorpha. This will raise two questions of mine later on, but I
will continue onward.
Okay, it's impossible for pterosaurs not to be ornithodirans, since
Ornithodira is defined as (Neornithes + Pterodactylus + Lagosuchus +
Herrerasaurus + Triceratops + Saltasaurus). So if pterosaurs are derived
prolacertiforms, Ornithodira just becomes more inclusive. But the
Ornithodira is also defined as (Neornithes --> Crocodylia), so in all
likelyhood, if pterosaurs were found to derived prolacertiforms, the latter
definition would be adopted.
Peters presents the following cladogram on his website, but I don't know if
it needs to be updated or not:
| |-- Prolacerta
| |-- Boreopricea
| |-- Jesairosaurus
| `-- "Tapinoplatia"
| |-- Macrocnemus
| `-- "Characiopoda"
| |-- Tanystropheidae
| `--+-- Langobardisaurus
| `-- "Fenestrasauria"
| |-- Cosesaurus
| |-- Longisquama
| `--+-- Sharovipteryx
| `-- Pterosauria
1. Low scapula grading to posterodorsally oriented and narrow scapula.
2. Short chevrons grading to anteriorly and sagittally oriented.
1. Elongated proximal phalanx of pedal digit V.
2. No more than five tarsals. Distal tarsal III very small.
3. Postcloacal bones on male.
1. Proportionately large skull more than half as long as the presacral
column (present at least in Longisquama, Sharovipteryx, and Pterosauria).
2. Elongated premaxillary dorsal process contacting the frontals.
3. Ulna and radius straight with little to no spatium interosseum (present
in Cosesaurus, Longisquama, and Pterosauria, presumedly reversed in
4. Tibia and fibula straight with little to no spatium interosseum.
5. Procoelous vertebrae.
6. Broad sternal complex formed of paired clavicles and sternal plates and
with a cristospine formed of the interclavicle.
7. Strut-shaped coracoid articulating with the cristospine of the sternum.
8. Manual digit V much reduced alongside unreduced digit IV.
9. Metatarsals appressed.
10. Preorbital fenestra (three primatively) closely associated with the
naris and without a fossa.
11. Maxilla extensively participating in the border of the external naris.
12. Quadratojugal spur forming the ventral margin of the lower temporal
13. Four sacral vertebrae.
14. Greatly reduced tranverse vertebral processes on caudals.
15. Hemal arches reduced.
16. Tall, narrow scapula oriented posterodorsally.
17. Coracoid grading from elliptical to strut-like.
18. Large postacetabular process of ilium.
19. Large, sharp preacetabular process of ilium.
20. Small overall adult size (14 cm to 25 cm). [Egh, I don't like this
If you are reading this HP Peters, could you please post what characters
indicate the paraphyly of Pseudosuchia and what permits Ornithosuchidae to
be the sistergroup of the clade containing Lagosuchus, Scleromochlus, and
Dinosauria. I'm very interested in knowing.
Also, I just found the following post of interest in the DML Archives:
2) Scleromochlus: What is it? Prolacertiform or a basal ornithodiran? (Or a
likely pterosaur ancestor)
According to M.J. Benton (1999), it is the outgroup to both Pterosauria and
the Dinosauromorpha, or in other words, it's neither, but instead a
-- Archosauria (= Avesuchia)
Scleromochlus is united with the Ornithodira by:
1. Forelimb-hindlimb ratio less than 55%.
2. Pubis longer than ischium.
3. Tibia-femur ratio more than 1.0.
4. Distal tarsal IV subequal in transverse width to distal tarsal III.
5. Compact metatarsus with metatarsals I-IV tightly bunched.
6. Metatarsals II-IV more than 50% tibial length.
7. Dorsal body osteoderms absent.
Pterosaurs and Dinosauromorphs are united to the exclusion of Scleromochlus
1. Presacral centrum 8 longer than presacral centrum 18.
2. Deltopectoral crest on humerus subrectangular.
3. Fibula tapering and calcaneum reduced in size.
4. Astragalar posterior groove.
5. Calcaneal tuber rudimentary or absent.
David Marjanovic posted on the DML the following message:
He points out the following characters to unite Pterosauria, Sharovipteryx,
1. Skull as least as large as ribcage. (Present in Longisquama [D. Peters,
online: "The Origin of the Pterosauria within the Prolacertiformes"])
2. Longer forearms (ulna and radius?) than upper arms (humerus?).
3. Longer humeri than scapulae.
4. Metatarsals I through IV closely bunched together.
5. Hook-shaped metatarsal V. (He admits it is plesimorphic)
Also of interest as far as systematic positions go, this post is rather
intriguing about Saltopus:
3) Protarchaeopteryx robusta: primitive oviraptorosaur like Caudipteryx, or
still "incertae sedis"?
I believe it is a basal oviraptorosaur, possibly related to Incisivosaurus,
with Caudipteryx closer to the other oviraptorosaurs, but this is basaed
only on similarities in the dentition of Incisivosaurus and
Protarchaeopteryx which have been already discussed on the list by other
Add photos to your messages with MSN 8. Get 2 months FREE*.