Tynskya waltonensis sp. nov. (1 Viewer)

[Fred Ruhe]

Gerald Mayr, 2021

A partial skeleton of a new species of Tynskya Mayr, 2000 (Aves, Messelasturidae) from the London Clay highlights the osteological distinctness of a poorly known early Eocene “owl/parrot mosaic”

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https://doi.org/10.1007/s12542-020-00541-8

Free pdf and abstract: https://link.springer.com/article/10.1007/s12542-020-00541-8

Tynskya eocaena is an early Eocene bird with a raptor-like skull and semi-zygodactyl feet, whose description is based on a skeleton from the North American Green River Formation. In the present study, three-dimensionally preserved bones of a new species of Tynskya, T. waltonensis, are reported from the London Clay of Walton-on-the-Naze (Essex, UK). The fossils belong to a single individual and provide new insights into the skeletal morphology of messelasturids. In particular, they reveal unusual vertebral specializations, with the cervical vertebrae having concave rather than saddle-shaped caudal articulation facets and the caudalmost thoracic vertebra being platycoelous (flat articular surfaces). The very deep mandible and a derived morphology of the ungual phalanges support a sister group relationship between Tynskya and the taxon Messelastur (Messelasturidae). Phylogenetic analyses of an emended data matrix did not conclusively resolve the higher-level affinities of messelasturids and the closely related halcyornithids, with both taxa sharing derived characters with only distantly related extant taxa (Accipitriformes, Strigiformes, Falconiformes, and Psittaciformes). An analysis that was constrained to a molecular scaffold, however, recovered messelasturids as the sister taxon of a clade including psittaciform and passeriform birds. The derived morphologies of the mandible and cervical vertebrae suggest specialized feeding adaptations of Tynskya, and messelasturids may have exploited a feeding niche, which is no longer available to extant birds.

Keywords Fossil birds · Tynskya waltonensis sp. nov. · Messelasturidae · Walton-on-the-naze · Ypresian

Enjoy,

Fred

 

[Fred Ruhe]

Systematic Paleontology

Aves Linnaeus, 1758
Messelasturidae Mayr, 2005

Genus Tynskya Mayr, 2000

Tynskya waltonensis sp. nov.

Holotype. SMF Av 652: partial skeleton comprising the left quadrate, a partial mandible, at least nine vertebrae, a cranial fragment of the sternum, a partial furcula, a partial left coracoid, the cranial ends of both scapulae, the proximal
end of the right humerus, the distal end of the left ulna, the proximal end of the right radius, the proximal end of the left carpometacarpus, the proximal end of the left femur, five pedal phalanges, and the left os metatarsale I (Fig. 1c); the fossil was found in 1986 by Paul Bergdahl (original collector’s number BC 8611).

Diagnosis. The new species differs from Tynskya eocaena in the shape of the processus acrocoracoideus of the coracoid, which is proportionally narrower, with the facies articularis clavicularis forming a better defined medial hook; the scapus of the furcula is furthermore not widened in its omal section and the tip of the processus extensorius of the carpometacarpus is somewhat more proximally directed. Messelastur gratulator is larger than both T. eocaena and T. waltonensis.

Type locality and horizon. Walton-on-the-Naze, Essex, United Kingdom; Walton Member of the London Clay Formation (previously Division A2; Jolley 1996; Aldiss 2012), early Eocene (early Ypresian; 54.6‒55 million years ago; Collinson et al. 2016).

Etymology. The species epithet refers to the type locality Walton-on-the-Naze.

Fred

Fig. 1 a, b Main slab (a) and counter slab (b) of the Tynskya eocaena holotype from the North American Green River Formation (SNSBBSPG 1997 I 6); note that most limb bones of the counter slab have been fabricated by the preparator of the fossil. c‒p Partial skeleton of Tynskya waltonensis sp. nov. from the early Eocene London Clay of Walton-on-the-Naze, Essex, UK (SMF Av 652); all bones are from a single individual, unidentifiable or uninformative fragments preserved in the specimen are not shown; c mandible, d left quadrate, e vertebrae, f left coracoid, g, h left and right scapula, i furcula, j fragment of sternum, k right humerus, l distal end of left ulna, m proximal end of right radius, n partial left carpometacarpus, o proximal end of left femur, p left os metatarsale I and pedal phalanges. Scale bars equal 20 mm for a and b and 5 mm for c‒p