Re-evaluation of the Haarlem Archaeopteryx and the radiation of maniraptoran theropod dinosaurs

Abstract

Background Archaeopteryx is an iconic fossil that has long been pivotal for our understanding of the origin of birds. Remains of this important taxon have only been found in the Late Jurassic lithographic limestones of Bavaria, Germany. Twelve skeletal specimens are reported so far. Archaeopteryx was long the only pre-Cretaceous paravian theropod known, but recent discoveries from the Tiaojishan Formation, China, yielded a remarkable diversity of this clade, including the possibly oldest and most basal known clade of avialan, here named Anchiornithidae. However, Archaeopteryx remains the only Jurassic paravian theropod based on diagnostic material reported outside China.ResultsRe-examination of the incomplete Haarlem Archaeopteryx specimen did not find any diagnostic features of this genus. In contrast, the specimen markedly differs in proportions from other Archaeopteryx specimens and shares two distinct characters with anchiornithids. Phylogenetic analysis confirms it as the first anchiornithid recorded outside the Tiaojushan Formation of China, for which the new generic name Ostromia is proposed here.ConclusionsIn combination with a biogeographic analysis of coelurosaurian theropods and palaeogeographic and stratigraphic data, our results indicate an explosive radiation of maniraptoran coelurosaurs probably in isolation in eastern Asia in the late Middle Jurassic and a rapid, at least Laurasian dispersal of the different subclades in the Late Jurassic. Small body size and, possibly, a multiple origin of flight capabilities enhanced dispersal capabilities of paravian theropods and might thus have been crucial for their evolutionary success.Electronic supplementary materialThe online version of this article (10.1186/s12862-017-1076-y) contains supplementary material, which is available to authorized users.

The Biogeography of Coelurosaurian Theropods and its Impact on their Evolutionary History

“…If intermediate coelurosaurian taxa from Gondwana are not derived from vicariance induced by Pangaean breakup, they most probably arrived from Laurasian landmasses. Although such 'Laurasian arrival' hypotheses have been suggested (Naish, et al, 2004;Foth and Rauhut, 2017), these biogeographic events were not linked by these authors to the only feasible Laurasia-Gondwana dispersal route known in the Early Cretaceous. In our results, many inferred dispersal events via the Apulian Route explain South American coelurosaurian occurrences of their Laurasian relatives, but discoveries of closely-related African taxa are lacking.…”

“…AVIALAE: This clade includes early birds and their modern descendants (Padian, 2004) and by the Late Cretaceous avialans had achieved a global geographic distribution (Brocklehurst, et al, 2012). The controversial Late Jurassic stem paravians, the anchiornithids, proposed as both stem birds and troodontids were previously only known from Liaoning, China (Godefroit, et al, 2013), but have recently been confirmed in Europe (Ostromia) (Foth and Rauhut, 2017). This might indicate a Late Jurassic dispersal event from Asia to Europe (Foth and Rauhut, 2017) given that Archaeopteryx, the most widely accepted oldest and most stemward bird, is from Germany (Wellnhofer, 2009;Foth, et al, 2014).…”

“…The controversial Late Jurassic stem paravians, the anchiornithids, proposed as both stem birds and troodontids were previously only known from Liaoning, China (Godefroit, et al, 2013), but have recently been confirmed in Europe (Ostromia) (Foth and Rauhut, 2017). This might indicate a Late Jurassic dispersal event from Asia to Europe (Foth and Rauhut, 2017) given that Archaeopteryx, the most widely accepted oldest and most stemward bird, is from Germany (Wellnhofer, 2009;Foth, et al, 2014). The second oldest avifaunas are in the Early Cretaceous Hauterverian -Barremian, in which the more crownward clades Ornithuromorpha and Enantiornithes first appear, are found in China (Zhou and Zhang, 2006) and Mongolia (O'Connor and Zelenkov, 2013;Zelenkov and Averianov, 2016) where both clades are represented, and in Spain, where only enantiornithines have been found (Sanz, 1990;Sanz, et al, 1995;Sanz, et al, 1996).…”

The fast and the frugal: Divergent locomotory strategies drive limb lengthening in theropod dinosaurs

“…Even at similar sizes the divergence between relative hindlimb versus distal limb metrics is clearly illustrated by comparing the Yixian biota contemporaries Changyuraptor and Sinosauropteyrx, both of which are suspected small carnivores that differ in length by 10mm (~ 2% total SVL). Changyuanraptor show a relative hindlimb index of 0.96, which is significantly higher than that is seen in Sinosauropteyrx Interestingly, amongst anchiornithids (a clade of small bodied paravians who have recently suggested to be more closely related to birds than either dromaeosaurids or troodontids [47,48]) we see a diverse pattern of values ranging from Anchiornis at the high end (92-95%) to Caihong (78%) at the lower end, though the latter is still similar to what is seen in the cursorial oviraptorosaur Caudipteryx (0.75-0.79). We calculated maximum speed potential with the larger hindlimb indices in many microraptorines allowing them to achieve higher top end speed suggesting a sharp demarcation between burst speed potential between microraptorines, contemporaneous small bodied compsognathids and basal birds (Figure 2, Sup.…”

The Dinosauria: Baraminological and multivariate patterns

“…We analyzed a Maniraptoran matrix in place of Weishampel's Oviraptorosauria. The matrix consisted of 560 characters for 132 taxa (Foth and Rauhut 2017). We examined both the complete dataset and the 46 taxa with at least 50% of their character states known.…”