Updated January 17, 2018 with a new tracing and nesting of Ostromia as a sister to Eosinopteryx in the proximal outgroup clade to the birds.
Updated June 23, 2109 with revised closeup images of the pelvis, ‘clavicle’ and pes.
A recent paper
by Foth and Rauhut 2017 reexamined the incomplete Haarlem specimen on plate and counter plate (TM 6928, 6929, Figs. 1–3) originally attributed to a pterosaur (Pterodactylus crassipes, von Meyer 1857) and later to Archaeopteryx crassipes (Ostrom 1970). The co-authors renamed the specimen Ostromia crassipes and nested it with Anchiornis (Fig. 2), a larger troodontid with a short coracoid outside of the bird clade in the large reptile tree (LRT).
Foth and Rauhut 2017
considered Anchiornis, “the possibly oldest and most basal clade of avialan, here named Anchiornithidae.” And they considered Ostromia the first and only anchiornithid outside of the Tiaojushan Formation of China.
The authors employed a previously published phylogenetic analysis
from Foth et al. 2014. which looked at the privately owned 11th specimen of Archaeopteryx. Unfortunately their cladogram lumped all Archaeopteryx specimens (Fig. 3) together. So we’re dealing with a possible taxonomic chimaera and a certain taxon exclusion.
The variety shown by the Solnhofen birds
(Fig. 3) should invite phylogenetic analysis (Fig. 4). But Foth et al. (2014, 2017) did not respond to the invitation. If they had done so, perhaps they would have replicated the results of the LRT in nesting Ostromia with other coeval Archaeopteryx specimens. Their Ostromia nests here with Eosinopteryx, not with Anchiornis.
In size, strata and morphology
Ostromia nests rather closely to the other Solnhofen birds in the LRT, but in the proximal outgroup, along with Eosinopteryx and Xiaotingia.
I encourage bird workers
to not lump the Solnhofen birds together as a single taxonomic unit, but to split them into individual specimens. There’s a treasure to be found there. Each one deserves to be its own species, if not its own genus.
Revised images in detail
Foth C and Rauhut OWM 2017. Re-evaluation of the Haarlem Archaeopteryx and the radiation of maniraptoran theropod dinosaurs. BMC Evolutionary Biology 17:236
Foth C, Tischlinger H, Rauhut OWM 2014. New specimen of Archaeopteryx provides insights into the evolution of pennaceous feathers. Nature 511:79–82.
Ostrom JH 1970. Archaeopteryx: notice of a “new” specimen. Science. 1970;170:537_538.
Von Meyer H 1861. Archaeopteryx lithographica und Pterodactylus. N Jb Min Geognosie Geol Petrefaktenkd. 1861:678–679.
TM = Teylers Museum in Haarlem, the Netherlands