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ornithodira characters for pterosaurs



Chris Collins wrote:

Can someone please give me a list of morphological characters used to
place
pterosaurs within the Ornithodira? Thanks.




Cheers,
Christopher

Sereno 1991 lists the following synapomorphies for the Ornithodira.

1. Dorsal body osteoderms absent.
2. Interclavicle absent
3. Clavicle rudimentary or absent
4. Femoral shaft bowed anteriorly along at least 80 percent of shaft
5. Tibia subequal or longer than femur.
6. Astragalar posterior groove absent
7. Calcaneal tuber rudimentary or absent.
8. Distal tarsal 4 transverse width subequal to distal tarsal 3
9. Metatarsals 1-4 shafts closely appressed
10. Metatarsal 2-4 length more than 50 percent tibia length

In addition, Sereno notes the following are putatively shared by
Scleromochlus and pterosaurs:

1. Skull length more than 50 percent presacral column length
2. Scapula length less than 75 percent of that of humerus
3. Fourth trochanter absent
4. Metatarsal I length 85 percent or more of metatarsal 3.

Not sure if anyone has modified this recently, but Benton 1999 came up
with a similar taxon concept, the Avemetatarsalia, including some from
the first list and adding the following:

1. Forelimb-hindlimb ratio less than 0.55
2. Pubis longer than ischium


David Peters
St. Louis