''Ostromia crassipes'' (''Thick-foot of

John Ostrom John Harold Ostrom (February 18, 1928 – July 16, 2005) was an American paleontologist who revolutionized the modern understanding of dinosaurs. Ostrom's work inspired what his pupil Robert T. Bakker has termed a " dinosaur renaissance". Begin ...

'') is the single

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of the

anchiornithid Anchiornithidae is a family of small paravian dinosaurs. Anchiornithids have been classified at varying positions in the paravian tree, with some scientists classifying them as a distinct family, a basal subfamily of Troodontidae, members of Arc ...

theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

genus ''Ostromia''. Recovered from the

Late Jurassic The Late Jurassic is the third Epoch (geology), epoch of the Jurassic Period, and it spans the geologic time scale, geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic stratum, strata.Owen ...

Painten Formation The Painten Formation is a geologic formation in Germany. It preserves fossils dating back to the Tithonian stage of the Late Jurassic period.Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

, it was named by Christian Foth and Oliver Rauhut in 2017.

Discovery and naming

The holotype was discovered near

Riedenburg Riedenburg () is a town in the district of Kelheim, in Bavaria, Germany. It is situated on the river Altmühl, northwest of Kelheim and northeast of Ingolstadt Ingolstadt (; Austro-Bavarian language, Austro-Bavarian: ) is an Independent ci ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

in 1855 and it was originally misidentified as a species of a pterodactyloid

pterosaur Pterosaurs are an extinct clade of flying reptiles in the order Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 million to 66 million years ago). Pterosaurs are the earli ...

and named ''

Pterodactylus ''Pterodactylus'' (from ) is a genus of extinct pterosaurs. It is thought to contain only a single species, ''Pterodactylus antiquus'', which was the first pterosaur to be named and identified as a flying reptile and one of the first prehis ...

crassipes'' in 1857. In 1970 it was identified as an ''

Archaeopteryx ''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird'') is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaîos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...

'' by paleontologist

, who called it the "Haarlem specimen", since it was kept in the

Teylers Museum Teylers Museum () is an Art museum, art, Natural history museum, natural history, and science museum in Haarlem, Netherlands. Established in 1778, Teylers Museum was founded as a centre for contemporary art and science. The historic centre of the ...

Haarlem Haarlem (; predecessor of ''Harlem'' in English language, English) is a List of cities in the Netherlands by province, city and Municipalities of the Netherlands, municipality in the Netherlands. It is the capital of the Provinces of the Nether ...

. In 2017 Christian Foth and Oliver Rauhut concluded it was more closely related to the

Chinese Chinese may refer to: * Something related to China * Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity **Han Chinese, East Asian ethnic group native to China. **'' Zhonghua minzu'', the supra-ethnic ...

Anchiornis ''Anchiornis'' is a genus of small, four-winged Paraves, paravian dinosaurs, with only one known species, the type species ''Anchiornis huxleyi'', named for its similarity to modern birds. The Latin name ''Anchiornis'' derives from a Greek word m ...

'' 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 In human anatomy, the metacarpal bones or metacarpus, also known as the "palm bones", are the appendicular bones that form the intermediate part of the hand between the phalanges (fingers) and the carpal bones ( wrist bones), which articulate ...

of the hand is larger in ''Ostromia'' than in any ''Archaeopteryx'' specimen. In addition, the

ungual An ungual (from Latin ''unguis'', i.e. ''nail'') is a highly modified distal toe bone which ends in a hoof, claw, or nail. Elephants and ungulates have ungual phalanges, as did the sauropod Sauropoda (), whose members are known as sauropods (; ...

(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 The metatarsal bones or metatarsus (: metatarsi) are a group of five long bones in the midfoot, located between the tarsal bones (which form the heel and the ankle) and the phalanges (toes). Lacking individual names, the metatarsal bones are nu ...

are also estimated to be proportionally longer than those of ''Archaeopteryx'' specimens. OSTROMIA mario lanzas recomstruction

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 The phalanges (: phalanx ) are digit (anatomy), digital bones in the hands and foot, feet of most vertebrates. In primates, the Thumb, thumbs and Hallux, big toes have two phalanges while the other Digit (anatomy), digits have three 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 In vertebrates, the pubis or pubic bone () forms the lower and anterior part of each side of the hip bone. The pubis is the most forward-facing (ventral and anterior) of the three bones that make up the hip bone. The left and right pubic bones ar ...

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 Unenlagiinae is a subfamily of long-snouted paravian theropods. They are traditionally considered to be members of Dromaeosauridae, though some authors place them into their own family, Unenlagiidae, sometimes alongside the subfamily Halszkar ...

, 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.

References

{{Portal bar, Dinosaurs, Germany Anchiornithidae Dinosaur genera Tithonian dinosaurs Fossil taxa described in 2017 Dinosaurs of Germany

Discovery and naming

Description

Differences from ''Archaeopteryx''

Classification

See also

References