Margarobyas abronensis sp. nov. (1 Viewer)

[Fred Ruhe]

Nikita V. Zelenkov & Soraida F. González, 2021

A new extinct species of Margarobyas (Strigiformes) and the evolutionary history of the endemic Cuban bare-legged owl (M. lawrencii)

Journal of Vertebrate Paleontology in press
e1995869. doi:10.1080/02724634.2021.1995869

ABSTRACT

The Cuban bare-legged owl (Margarobyas lawrencii) is a poorly studied bird of uncertain affinities within Strigidae (true owls). Molecular data indicate that M. lawrencii may be one of the earliest diverging lineages of crown group Strigidae, but the evolutionary history of this taxon remains obscure. Here we describe a fossil species of Margarobyas from the Upper Pleistocene of Western Cuba and for the first time address the comparative osteology of this genus. The osteological survey confirms the remarkable morphological distinctiveness of the modern Margarobyas lawrencii. Margarobyas displays a derived similarity to Ninox owls (hawk-owls, subfamily Ieraglaucinae) in the morphology of the quadratum, but in the overall morphology of the skeleton it is also similar to members of the subfamily Striginae and species of Megascops (screech owls) in particular. The mixture of characters of both Striginae and Ieraglaucinae implies an early (no later than Oligocene) divergence of Margarobyas, thus supporting a long evolutionary history of these owls compared with other endemic owl species of the West Indies. The antiquity of Margarobyas makes it, along with Todidae (todies), one of the most archaic components of the modern West Indian avifauna.

The paper describes Margarobyas abronensis sp. nov.

Enjoy,

Fred

 

[Fred Ruhe]

SYSTEMATIC PALEONTOLOGY

Order STRIGIFORMES Wagler, 1830
Family STRIGIDAE Leach, 1820

The new taxon can be attributed to Strigidae because it is morphologically similar, as outlined in the comparative osteological
section above, to the extant Margarobyas lawrencii, which was recovered within Strigidae in a recent molecular analysis (Salter et al., 2020). Both new extinct species and the extant M. lawrencii further share many osteological similarities with various strigid owls (especially, the genera Megascops and Ninox; see above).

Genus MARGAROBYAS Olson and Suarez, 2008
MARGAROBYAS ABRONENSIS, sp. nov.
urn:lsid:zoobank.org:actC8CACCE-69B3-4338-82A1-E93B20A7F7DC

Holotype—Complete left tarsometatarsus, PIN 5781/14, collected by the joint MNHN and PIN expedition in 2019.

Type Locality—El Abrón Cave (layer VII); Pinar-del-Río Province, Cuba. Upper Pleistocene.

Etymologie— Not given in the paper, but I suppose it is named after the Type Locality, El Abrón Cave.

Referred Material—All from the type locality. Layer V: right quadratum (PIN 5781/2), right coracoid (PIN 5781/3), left scapula (PIN 5781/5), left humerus (PIN 5781/17), right humerus (PIN 5781/18), right tibiotarsus (PIN 5781/19), left tarsometatarsus (PIN 5781/20). Layer VI: maxilla (PIN 5781/1), right coracoid (PIN 5781/4), right and left distal humeri (PIN 5781/21, 22), left proximal ulna (PIN 5781/23). Layer VII: complete left and right coracoids (PIN 5781/24, 25), left and right scapulae (PIN 5781/26, 27), left and right complete humeri (PIN 5781/6, 7), left complete ulna (PIN 5781/8), right and left carpometacarpi (PIN 5781/9, 10), left femur (PIN 5781/11), left and right tibiotarsi (PIN 5781/12, 13), left and right tarsometatarsi (PIN 5781/15, 16). Layer VIII: left coracoid (PIN 5781/28), right scapula (PIN 5781/29), proximal left humerus (PIN 5781/29), left carpometacarpus (PIN 5781/30). Layer IX: right coracoid (PIN 5781/31), left scapula (PIN 5781/32), right carpometacarpus (PIN 5781/33), and right tarsometatarsus (PIN 5781/34).

Diagnosis—Slightly smaller than extant M. lawrencii (Table 1). Further differs from M. lawrencii in having:maxilla shorter; caudal isolated foramen of bony nostrils positioned very close to the caudal margin of the upper bill; bony strut dividing the main cavity of the bony nostril and its caudal foramen poorly developed; rostral parts of palatines and the lateral bony bars bordering the fenestra ventromedialis narrow. Coracoid with somewhat craniocaudally shorter processus acrocoracoideus than in M. lawrencii. Humerus slightly to moderately shorter than in M. lawrencii; fossa brachialis closely attached to ventral margin of the shaft. Carpometacarpus smaller than in M. lawrencii with metacarpalia minor poorly protruding distally relative to metacarpalia major; ventrally directed tuberculum on the base of metacarpalia minor is more prominent and distinct. Shaft of femur almost straight. Tibiotarsus craniocaudally lower than in M. lawrencii in distal view; incisura intercondylaris wider; sulcus cartilaginis tibialis shallow. Tarsometatarsus proportionally longer than in M. lawrencii with approximately the same length of the bone but narrower shaft and articular ends (especially the proximal one); almost straight in medial/lateral view (concavity of the dorsal margin poorly pronounced); crista lateralis hypotarsi points predominately plantarly; trochlea metatarsi II (excluding wing-like medial extension) smaller in distal view.

Fred


FIGURE 1. Cranial elements of Margarobyas and selected species of Strigidae. A, F, K, P, Q, Margarobyas abronensis, sp. nov., Upper Pleistocene of El Abrón Cave, Western Cuba: A, F, specimen PIN 5781/1; K, P, Q, specimen PIN 5781/2; B, G, L, Margarobyas lawrencii, extant,
specimen PIN 108-100-1; C, H, M, Ninox scutulata, extant, specimen PIN 108-86-1; D, I, O, Megascops asio, extant, specimen PIN 108-22-1; E, J, N, Athene cunicularia, extant, specimen PIN 108-105-1. A–J, rostra in lateral (A–E) and ventral (F–J) views; K–Q, quadrati in caudal (K–O), lateral (P) and ventral (Q) views. Abbreviations: bs, bony strut separating caudal portion of bony nostrils; co, capitulum oticum; cs, capitulum squamosum; fv, fenestra ventromedialis; ss, shallow ventral surface of bony nostrils; vi, vallecula intercapitularis.

FIGURE 2. Coracoids and scapulae of Margarobyas and selected species of Strigiformes. A, B, H, I, M, O, Margarobyas abronensis, sp. nov., Upper Pleistocene of El Abrón Cave, Western Cuba: A, H, specimen PIN 5781/3; B, I, specimen PIN 5781/4; M, O, specimen PIN 5781/5; C, J, N, Margarobyas lawrencii, extant, specimen PIN 108-100-1; D, Megascops asio, extant, specimen PIN 108-22-1; E, Ninox scutulata, extant, specimen PIN 108-86-1; F, Glaucidium siju, extant, specimen
PIN 108-68-1; G, Athene cunicularia, extant, specimen PIN 108-105-2; K, Strix uralensis, extant, specimen PIN 109-10-2; L, Tyto alba, extant, specimen PIN 106-2-1. A–L, coracoids in ventral (A–J, K, L) and dorsal (H–J) views; M, N, scapulae in lateral view; O, scapula in medial view. Abbreviations: fas, facies articularis sternalis; ib, impressio bicipitalis; lea, lamina elliptica articularis; pa, processus acrocoracoideus; pp, processus procoracoideus. Scale bars equal 1 cm.