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Ostromia Temporal range: Early Tithonian ~150.8–145.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N
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
†O. crassipes (Meyer, 1857)
Synonyms
Pterodactylus crassipes Meyer, 1857 Rhamphorhynchus crassipes (Meyer, 1857) Scaphognathus crassipes (Meyer, 1857) Wagner, 1861 Archaeopteryx crassipes (Meyer, 1857) Ostrom, 1970

Ostromia (Thick feet of John Ostrom) is a genus of anchiornithid theropod dinosaur from the Late Jurassic Painten Formation of Germany. The genus contains a single species, O. crassipes, named by Christian Foth and Oliver Rauhut in 2017.

Discovery and naming

The holotype was discovered near Riedenburg, Germany in 1855 and it was originally misidentified as a species of a pterodactyloid pterosaur and named Pterodactylus crassipes in 1857. In 1970 it was identified as an Archaeopteryx by paleontologist John Ostrom, who called it the "Haarlem specimen", since it was kept in the Teylers Museum in Haarlem. In 2017 Christian Foth and Oliver Rauhut concluded it was more closely related to the Chinese Anchiornis and introduced the generic name Ostromia, named after Ostrom.

The only known specimen is fairly incomplete compared to most specimens of Archaeopteryx, 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 the Bayerische Staatssammlung für Paläontologie und Geologie under the specimen number SNSB-BSPG 1971 I 211.

Description

Differences from Archaeopteryx

The Haarlem specimen has many features which contrast with those of Archaeopteryx. The length ratio between the third and the first metacarpal of the hand is larger in Ostromia than in any Archaeopteryx specimen. In addition, the ungual (claw) of the first digit of the hand is smaller than the corresponding first metacarpal, while in Archaeopteryx the claw is larger. The Haarlem specimen's metatarsals are also estimated to be proportionally longer than those of Archaeopteryx specimens.

In addition, the Haarlem specimen shares several features with Anchiornis. Most notably, they both have longitudinal furrows on the top and bottom sides of their manual phalanges (finger bones). While such structures can be a result of collapsed or broken bones (as is the case in several Archaeopteryx specimens), the straight, smooth edges of the furrows in Ostromia and Anchiornis indicate that they are legitimate biological features. The pubic shaft of the Haarlem specimen is also strongly flexed backwards and has a triangular pubic boot, similar to the pubis of Anchiornis but unlike that of Archaeopteryx.

Classification

Foth and Rauhut (2017) recovered Ostromia within Anchiornithidae as the only known European member of this family. Agnolin et al. (2019) argued that the putative anchiornithid affinities of Ostromia are also seen in Unenlagiinae, and that it is best to consider this genus as an indeterminate paravian. In contrast, Foth et al. (2025) still recovered the same conclusion that Ostromia is an anchiornithid based on their phylogenetic analysis.

See also

• 2017 in archosaur paleontology

References

1. Ostrom JH. Archaeopteryx: notice of a “new” specimen. Science. 1970;170:537–8
2. ^ Foth, C.; Rauhut, O.W.M. (2017). "Re-evaluation of the Haarlem Archaeopteryx and the radiation of maniraptoran theropod dinosaurs". BMC Evolutionary Biology. 17 (1): 236. doi:10.1186/s12862-017-1076-y. PMC 5712154. PMID 29197327.
3. Agnolín, Federico L.; Motta, Matias J.; Brissón Egli, Federico; Lo Coco, Gastón; Novas, Fernando E. (2019-02-12). "Paravian Phylogeny and the Dinosaur-Bird Transition: An Overview". Frontiers in Earth Science. 6. doi:10.3389/feart.2018.00252. hdl:11336/130197. ISSN 2296-6463.
4. Foth, Christian; van de Kamp, Thomas; Tischlinger, Helmut; Kantelis, Theron; Carney, Ryan M.; Zuber, Marcus; Hamann, Elias; Wallaard, Jonathan J. W.; Lenz, Norbert; Rauhut, Oliver W. M.; Frey, Eberhard (3 January 2025). "A new Archaeopteryx from the lower Tithonian Mörnsheim Formation at Mühlheim (Late Jurassic)". Fossil Record. 28 (1): 17–43. doi:10.3897/fr.28.e131671.

v t e Maniraptora
Kingdom: Animalia Phylum: Chordata Clade: Dinosauria Clade: Theropoda Clade: Maniraptoriformes Avemetatarsalia see Avemetatarsalia Theropoda see Theropoda Maniraptora see below↓
Maniraptora Maniraptora †Elopteryx? †Fukuivenator? †Kakuru? †Migmanychion †Yaverlandia? †Alvarezsauroidea Achillesaurus Aorun? Bannykus Bonapartenykus Haplocheirus Patagonykus Shishugounykus Tugulusaurus? Xiyunykus Alvarezsauridae Achillesaurus? Alnashetri Alvarezsaurus Bonapartenykus? Bradycneme Heptasteornis Patagonykus? Parvicursorinae Dzharaonyx Jaculinykus Khulsanurus Kol? Nemegtonykus Ondogurvel Parvicursor Qiupanykus Trierarchuncus Ceratonykini Albinykus Ceratonykus Xixianykus Mononykini Albertonykus Linhenykus Mononykus Shuvuuia †Therizinosauria Eshanosaurus? Falcarius Fukuivenator? Jianchangosaurus Lingyuanosaurus Therizinosauroidea Alxasaurus Beipiaosaurus Enigmosaurus Martharaptor Suzhousaurus Therizinosauridae Erliansaurus Erlikosaurus Nanshiungosaurus Neimongosaurus Nothronychus Paralitherizinosaurus Segnosaurus Therizinosaurus Pennaraptora †Oviraptorosauria see Oviraptorosauria Paraves see below↓
Paraves Paraves †Palaeopteryx? †Pneumatoraptor †Rahonavis †Scansoriopterygidae? Ambopteryx Epidexipteryx Scansoriopteryx Yi †Anchiornithidae Anchiornis Aurornis Caihong Eosinopteryx Fujianvenator Liaoningvenator? Ostromia Pedopenna Serikornis Xiaotingia Yixianosaurus †Archaeopterygidae Alcmonavis? Archaeopteryx Wellnhoferia Anchiornithidae? †Dromaeosauridae see Dromaeosauridae †Troodontidae see Troodontidae Avialae †Alcmonavis †Balaur? †Cretaaviculus? †Fukuipteryx †Overoraptor †Rahonavis? †Yandangornis †Zhongornis †Anchiornithidae? †Archaeopterygidae? †Scansoriopterygidae? †Jeholornithiformes Dalianraptor? Jeholornis Jixiangornis? Kompsornis Neimengornis Pygostylia †"Proornis" †Omnivoropterygidae? Omnivoropteryx Sapeornis †Confuciusornithidae Changchengornis Confuciusornis Eoconfuciusornis Yangavis †Jinguofortisidae Chongmingia Cratonavis Jinguofortis Ornithothoraces †Enantiornithes see Enantiornithes Euornithes see below↓
Euornithes Euornithes †Archaeorhynchus †Bellulornis †Brevidentavis †Changmaornis †Changzuiornis †Chaoyangia †Dingavis †Eogranivora †Gargantuavis? †Hollanda †Horezmavis †Jianchangornis †Jiuquanornis †Juehuaornis †Kaririavis †Meemannavis †Platanavis †Vorona †Wyleyia? †Xinghaiornis †Yumenornis †Zhongjianornis †Schizoouridae Mengciusornis Schizooura †Patagopterygiformes Alamitornis Kuszholia? Patagopteryx †Ambiortiformes Ambiortus Apsaravis? Palintropus? †Hongshanornithidae Archaeornithura Hongshanornis Longicrusavis Parahongshanornis Tianyuornis †Songlingornithidae Hollanda? Piscivoravis? Songlingornis Yanornis? Yixianornis? †Yanornithidae Abitusavis Similiyanornis Yanornis †Gansuidae? Changzuiornis Gansus Hollanda? Iteravis Khinganornis Shuilingornis Ornithurae †Antarcticavis? †Apatornis †Cerebavis †Gallornis †Guildavis †Iaceornis †Kookne †Limenavis †Tingmiatornis †Ichthyornithes Ichthyornis Janavis †Hesperornithes Baptornis Brodavis Chupkaornis Enaliornis Judinornis Pasquiaornis Potamornis Hesperornithidae Asiahesperornis Canadaga Fumicollis Hesperornis Parahesperornis †Vegaviidae Australornis? Maaqwi? Neogaeornis? Polarornis Vegavis †Cimolopterygidae Ceramornis Cimolopteryx Lamarqueavis? Aves / Neornithes see below↓
Aves / Neornithes Palaeognathae see Palaeognathae Neognathae Neoaves Galloanserae Anserimorphae see Anserimorphae Pangalliformes see Pangalliformes Incertae sedis †Asteriornis †Perplexicervix †Qinornis? †Dromornithidae Barawertornis Dromornis Genyornis Ilbandornis †Gastornithiformes Brontornis? Gastornis Dromornithidae? †Pelagornithidae Aequornis Caspiodontornis Cyphornis Dasornis Gigantornis Laornis? Lutetodontopteris Macrodontopteryx Manu? Odontopteryx Odontoptila Osteodontornis Palaeochenoides Pelagornis Proceriavis? Protodontopteryx Protopelicanus? Pseudodontornis Tympanonesiotes
See also: Archaeornithes Carinatae Deinonychosauria Odontognathae Odontornithes Sauriurae Unenlagiidae Category

• Dinosaurs
• Germany

• Anchiornithidae
• Monotypic dinosaur genera
• Late Jurassic dinosaurs of Europe
• Jurassic Germany
• Fossils of Germany
• Solnhofen fauna
• Fossil taxa described in 2017
• Taxa named by Christian Erich Hermann von Meyer