| Ostromia | |
|---|---|
 | |
| Slabs of the type and only specimen | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Anchiornithidae |
| Genus: | †Ostromia Foth & Rauhut, 2017 |
| Type species | |
| †Pterodactylus crassipes Meyer, 1857 | |
| Species | |
| Synonyms | |
| |
Ostromia crassipes (Thick-foot ofJohn Ostrom) is the singlespecies of theanchiornithidtheropoddinosaurgenusOstromia. Recovered from theLate JurassicPainten Formation ofGermany, it was named by Christian Foth and Oliver Rauhut in 2017.
The holotype was discovered nearRiedenburg,Germany in 1855 and it was originally misidentified as a species of a pterodactyloidpterosaur and namedPterodactylus crassipes in 1857. In 1970 it was identified as anArchaeopteryx by paleontologistJohn Ostrom, who called it the "Haarlem specimen", since it was kept in theTeylers Museum inHaarlem.[1] In 2017 Christian Foth and Oliver Rauhut concluded it was more closely related to theChineseAnchiornis and introduced the generic nameOstromia, named after Ostrom.[2]
The only known specimen is fairly incomplete compared to most specimens ofArchaeopteryx, as it only preserves limb bones, cervical vertebrae and ribs. Most bones are also incomplete, as a result of the poor preservation. A high-quality cast of the holotype (Teylers specimens TM 6928 and 6929) is in the collections of theBayerische Staatssammlung für Paläontologie und Geologie under the specimen number SNSB-BSPG 1971 I 211.[2]
The Haarlem specimen has many features which contrast with those ofArchaeopteryx. The length ratio between the third and the firstmetacarpal of the hand is larger inOstromia than in anyArchaeopteryx specimen. In addition, theungual (claw) of the first digit of the hand is smaller than the corresponding first metacarpal, while inArchaeopteryx the claw is larger. The Haarlem specimen'smetatarsals are also estimated to be proportionally longer than those ofArchaeopteryx specimens.[2]
In addition, the Haarlem specimen shares several features withAnchiornis. Most notably, they both have longitudinal furrows on the top and bottom sides of their manualphalanges (finger bones). While such structures can be a result of collapsed or broken bones (as is the case in severalArchaeopteryx specimens), the straight, smooth edges of the furrows inOstromia andAnchiornis indicate that they are legitimate biological features. Thepubic shaft of the Haarlem specimen is also strongly flexed backwards and has a triangular pubic boot, similar to the pubis ofAnchiornis but unlike that ofArchaeopteryx.[2]
Foth and Rauhut (2017) recoveredOstromia within Anchiornithidae as the only known European member of this family.[2] Agnolin et al. (2019) argued that the putative anchiornithid affinities ofOstromia are also seen inUnenlagiinae, and that it is best to consider this genus as an indeterminate paravian.[3] In contrast, Foth et al. (2025) still recovered the same conclusion thatOstromia is an anchiornithid based on their phylogenetic analysis.[4]
.jpg)
