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Parapsittacopes bergdahli gen. et sp. nov. (1 Viewer)

Fred Ruhe

Well-known member
Netherlands
Gerald Mayr, 2021

A remarkably complete skeleton from the London Clay provides insights into the morphology and diversity of early Eocene zygodactyl near-passerine birds

Journal of Systematic Palaeontology. Online edition.
doi:10.1080/14772019.2020.1862930

Absytact: https://www.tandfonline.com/doi/full/10.1080/14772019.2020.1862930

Recognition of the zygodactyl parrots (Psittaciformes) as the closest extant relatives of passerines (Passeriformes) shed new light on the affinities of various Paleogene birds with a zygodactyl foot, which are now considered to be stem group representatives of the Passeriformes. However, most of these taxa are known only from compression fossils, which allow the recognition of a limited number of osteological details. Here, an exceptionally complete skeleton of a new species is described from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). Parapsittacopes bergdahli gen. et sp. nov. resembles Psittacopes lepidus (Psittacopedidae) from the Messel fossil site in Germany, from which it is distinguished in beak shape and several postcranial characters. Even though the phylogenetic analyses yielded conflicting tree topologies under different settings, all of the resultant phylogenies supported close affinities between Parapsittacopes, Psittacopes and the Eocene taxa Pumiliornis and Morsoravis. The three-dimensionally preserved bones of the P. bergdahli holotype exhibit subtle osteological characteristics of passeriform birds, which have not been reported from previously known fossils of closely related zygodactyl stem group taxa. The broad beak and low mandibular rami indicate that P. bergdahli may have caught insects by sallying flights from perches, and the new species therefore adds another feeding adaptation to the already diverse array of zygodactyl stem group Passeriformes with disparate feeding ecologies.

http://zoobank.org:pub:FD0E9DC4-961F-4460-9466-164E5EB42E4E

Enjoy,

Fred
 

Fred Ruhe

Well-known member
Netherlands
Hi Fred, do you have access to the paper?
Yes, I am lucky, a good friend and BirdForum member downloaded it for me this evening. Tomorow I will give more details. If I would not have had this luck, I wouls send Gerald Mayr a mail asking him for the paper, what in the past he always did.

Fred
 

Fred Ruhe

Well-known member
Netherlands
Systematic palaeontology

Aves
Linnaeus, 1758
Pan-Passeriformes sensu Mayr & Manegold (2006)
cf. Psittacopedidae Mayr, 2015
Parapsittacopes gen. nov.

Type species. Parapsittacopes bergdahli n. sp.

Diagnosis. Parapsittacopes gen. nov. is characterized by: beak short and wide, with large nostrils and slightly decurved tip; quadrate with pneumatic foramina on caudal surface of tip of processus oticus; mandible with dorsoventrally low rami and very short symphysis; thoracic vertebrae pleurocoelous; coracoid with incisura nervi supracoracoidei; scapula with very long and pointed acromion; sternum with cranially protruding apex carinae; humerus with well-defined tuberculum supracondylare dorsale; ulna with distal end of cotyla dorsalis forming a narrow, stripe-like mediodistal extension; ulna, distal end with craniocaudal constriction; radius with dorsal portion of distal end forming a proximally directed hook; phalanges of second toe much thinner than those of third toe.

Differential diagnosis. Parapsittacopes gen. nov. differs from:

Psittacopes in: beak with proportionally larger nostrils and shorter rostrum maxillare; mandible without large fenestra caudalis; apex carinae of sternum more pointed and protruding farther cranially; phalanges of second toe proportionally narrower

Pumiliornis in: beak proportionally shorter and wider; scapula with proportionally longer acromion; coracoid with narrower processus procoracoideus and more deeply excavated cotyla scapularis.

Eofringillirostrum in: upper beak not ‘finch-like’ and with proportionally larger nostril; mandibular rami less deep dorsoventrally and mandible without processus retroarticularis; scapula with longer acromion; second toe proportionally narrower and with proportionally longer proximal phalanx; ungual phalanges of anterior toes proportionally shorter.

all taxa of the Zygodactylidae in: beak proportionally wider; carpometacarpus with much smaller processus intermetacarpalis and proportionally larger trochlea carpalis; trochlea metatarsi III of tarsometatarsus with lateral tubercle.

Morsoravis in: beak proportionally shorter and wider; mandibular rami less deep dorsoventrally; quadrate with longer condylus lateralis and with pneumatic foramina in caudal surface of processus oticus; phalanges of second toe proportionally narrower; ungual phalanges with wider and less defined sulcus neurovascularis.

Eocuculus in: humerus more slender and distal end more slanting and with well-defined tuberculum supracondylare dorsale; phalanx proximalis digiti majoris without processus internus indicis.

Derivation of name. From para (Greek), next to, and Psittacopes, the type genus of the Psittacopedidae, which the new taxon closely resembles.

Parapsittacopes bergdahli gen. et sp. nov.

Holotype. SMF Av 653, a partial skeleton including the skull, right lacrimal, partial left and right quadrates, lower mandible, several vertebrae, partial right coracoid, right scapula and partial left scapula, sternal extremity of furcula, cranial portion of sternum, right humerus lacking distal end, distal end of left humerus, left ulna, right ulna lacking distal portion, distal ends of both radii, proximal end of right radius, proximal portion of left carpometacarpus, some wing phalanges, right half of pelvis, substantial portions of both femora, proximal end of left tibiotarsus and shaft fragment of right tibiotarsus, fragment of distal end of the right tarsometatarsus, shaft section of ?right tarsometatarsus, right os metatarsale I, 17 pedal phalanges or fragments thereof, as well as a block of matrix with partially exposed bones and numerous isolated and mostly unidentifiable bone fragments. The fossil was found in 1989 by Paul Bergdahl (original collector’s number BC 8917A).

Diagnosis. As for genus.

Derivation of name. The species is named after the late Paul Bergdahl (Kirby-le-Soken, UK), who collected the holotype.

Type locality and horizon. Walton-on-the-Naze, Essex, UK; 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).

Measurements (in mm). Skull, 23.5; length of upper beak, 10. Right quadrate, length from processus oticus to condylus medialis, 5.2. Right coracoid, estimated total length, 17.5. Right scapula, 24.2. Right humerus, length as preserved, 18.1; estimated total length, 23–24; proximal width, 7.6. Left humerus, distal width, 5.2. Left ulna, length, 24.8. Left femur, length as preserved, 17.1; estimated total length, 21. Tarsometatarsus, length as preserved, 13.9. Pedal phalanges: III1, 5.0; IV1, 3.2.

Fred

Figure 1. Parapsittacopes bergdahli gen. et sp. nov. from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK), cranial bones of the holotype (SMF Av 653). A–D, Skull in A, dorsal, B, ventral, C, right lateral and D, left lateral views. E, F, mandible in E, dorsal and F, ventral views. G, Bombycilla garrulus (Passeriformes, Bombycillidae), skull in dorsal view. H, skull of Psittacopes lepidus (holotype, SMF-ME 1279; picture taken through the reverse of the transparent resin slab into which the fossil is embedded). I–K, right lacrimal in I, cranial; J, caudomedial and K, dorsal views. L, M, proximal end of left mandibular ramus in L, ventral and M, dorsal views. N, Bombycilla garrulus, proximal end of left mandible in dorsal view. O–Q, fragment of proximal section of left mandibular ramus in O, dorsomedial, P, lateral and Q, ventrolateral views; the frame shows a detail with the fenestra caudalis. Abbreviations: ctl, cotyla lateralis; dsp, descending process (processus ventralis); faf, facies articularis frontonasalis; fam, fossa aditus canalis mandibulae; fcd, fenestra caudalis; gon, gonys; pco, processus coronoideus; ppo, processus postorbitalis; pzg, processus zygomaticus; sup, processus supraorbitalis. Scale bars equal 5mm.
 

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ZEISS. Discover the fascinating world of birds, and win a birding trip to Columbia
ZEISS. Discover the fascinating world of birds, and win a birding trip to Columbia
ZEISS. Discover the fascinating world of birds, and win a birding trip to Columbia

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