Glaucidium kurochkini, Campbell & Jr. & Bochenski, 2013

Campbell, Kenneth E., Jr. & Bochenski, Zbigniew M., 2013, Two new late Pleistocene miniature owls from Rancho La Brea, California, Acta Palaeontologica Polonica 58 (4), pp. 707-721 : 712-717

Glaucidium kurochkini sp. nov.

Figs. 1, 3, 4 .

Etymology: Dedicated to our late friend and colleague Evgeny N. Kurochkin, ornithologist and paleornithologist of the Paleontological Institute of the Russian Academy of Sciences, for his leading role in Russian ornithology and his many important contributions to our understanding of avian evolution.

Type material: Holotype: Complete left tarsometatarsus, LACM RLB K9630 . Paratypes: LACM (CIT) 155031, complete left tarsometatarsus ; LACM (CIT) 155032, complete right tarsometatarsus (both from Carpinteria , California) .

Type horizon: Rancho La Brea asphalt deposits; upper Pleistocene .

Type locality: Pit A of Bliss 29, Los Angeles, California, USA .

Diagnosis.—The tarsometatarsus of Glaucidium kurochkini ( Fig. 1) agrees with that of Glaucidium and differs from that of Aegolius by having those characters of Glaucidium listed above. Glaucidium kurochkini is diagnosed by the following characters of the tarsometatarsus: (1) Crista lateralis hypotarsi short, broad, robust, and projecting equally proximad and laterad (long, slender, and projecting more proximad than laterad in G. californicum and G. gnoma ; in G. ridgwayi , longer, more slender, and projecting more laterad than in G. californicum and G. gnoma , but less than in G. kurochkini ); (2) Eminentia intercotylaris long anteroposteriorly (moderately long to short anteroposteriorly in G. californicum and G. gnoma ; short anteroposteriorly in G. ridgwayi ); (3) Cotyla medialis with rim, in anterior view, essentially even with side of shaft (rim overhanging side of shaft in G. californicum and G. gnoma , but even with or slightly overhanging edge of shaft in G. ridgwayi ); (4) Fac. medialis wide proximally lateral to Crista medialis hypotarsi (narrow proximally in G. californicum , G. gnoma , and G. ridgwayi ); (5) Sulcus extensorius does not extend distal to Tuberositas m. tibialis anticus (Sulcus extensorius extends distad as a narrow groove between medial edge of Fac. dorsalis and Tuberositas m. tibialis anticus in G. californicum , G. gnoma , and G. ridgwayi ); and (6) Trochlea metatarsi II with anterior medial edge (side) relatively straight, in anterior view (medial edge with distinct notch in G. californicum and G. gnoma ; notched in G. ridgwayi , but not as much as in G. californicum and G. gnoma ).

Referred material.—The following specimens from Rancho La Brea are referred to Glaucidium kurochkini , but because they were not found in articulation or close association with the holotype it cannot be conclusively demonstrated that they represent that species. Therefore, we exclude them from the type series. Proximal left mandible, K9631 (Pit A); proximal right mandible, K9632 (Bliss 29); complete right coracoid, K9210 (Pit A); complete left humerus, G50 (Pit 16); proximal end of right radius, K9635 (Pit A); complete right carpometacarpus, K9404 (Bliss 29); complete left femur, K9350 (Pit A); complete left tibiotarsus, K984 (Pit 36); distal ends of three left tibiotarsi, K9402, K9422, K9423 (all Bliss 29).

Description and comparison.—All of the specimens described below agree with the characters given above that distinguish Glaucidium from Aegolius . The geographic distribution of the extant species of Glaucidium californicum , G. gnoma , and G. ridgwayi make them the most obvious candidate extant species to be represented by the fossil specimens from Rancho La Brea. Therefore, the most detailed comparisons of the fossils are with comparable elements of those three species. For measurements, see Table 1.

For the non−North American species of Glaucidium , the tarsometatarsus of G. kurochkini differs in size from those of G. cuculoides , G. radiatum , and G. perlatum , which are much larger species, and G. passerinum and G. minutissimum , which are much smaller species. Although of approximately the same length, it differs from that of G. brodiei in being more robust in all of its features, but it is similar in size and robustness to that of G. peruanum . Of the characters listed above that distinguish the tarsometatarsus of G. kurochkini from those of G. californicum , G. gnoma , and G. ridgwayi , all non−North American species agree with G. kurochkini for (1), except G. brodiei , in which the Crista lateralis hypotarsi is much less robust and smaller, projecting less both proximad and laterad, and G. peruanum , in which the Crista lateralis hypotarsi resembles that of G. ridgwayi . All have (2) Eminentia intercotylaris shorter anteroposteriorly. All have (3) Cotyla medialis with rim, in posterior view, essentially even with side of shaft, except G. brodiei in which it is slightly overhanging. Both characters (4) and (5) varied among the five species, and all had Trochlea metatarsi II (6) with anterior medial edge relatively straight, except G. radiatum and G. peruanum , in which it was notched. It is acknowledged that among the 25 species of Glaucidium and nine species of Taenioglaux currently living and recognized by König and Weick (2008), it might very well be possible to find one that closely resembles G. kurochkini in most osteological characters of the tarsometatarsus, although it would have to be a non−North American species. It is highly improbable, however, that if such a species exists on another continent that it would be represented by the Rancho La Brea taxon.

The mandible of Glaucidium kurochkini ( Fig. 3) differs from that of G. californicum , G. gnoma , and G. ridgwayi by having (1) Fac. artic. quadratica medialis with distal−medial edge straight (curves proximad, or posteriad, to meet Proc. mandibulae medialis in G. californicum , G. gnoma and G. ridgwayi ); (2) Fac. artic. quadratica medialis extending as narrow “tongue” mediad onto Proc. mandibulae medialis, where it gradually fades away (does not extend onto Proc. mandibulae medialis in G. californicum , G. gnoma , and G. ridgwayi , and medial edge is well marked); and (3) ridge for attachment of M. depressor mandibulae on ventral surface of Proc. mandibulae medialis rises abruptly from process at medial end and is broad based, but with high, narrow crest (ridge rises gradually from Proc. mandibulae medialis in G.

http://dx.doi.org/10.4202/app.2011.0125

californicum , G. gnoma , and G. ridgwayi , with a narrower base and a moderately high, narrow crest in G. californicum and G. gnoma and a moderately narrower base and a less prominent crest in G. ridgwayi ).

The one known coracoid of Glaucidium kurochkini ( Fig. 3) is very abraded. It differs from the coracoids of G. californicum , G. gnoma , and G. ridgwayi by having (1) Proc. acrocoracoideus thinner dorsoventrally (although some breakage on tip affects appearance); (2) area between rim of Fac. artic. humeralis and bicipital attachment only slightly concave, in ventrolateral and ventral view (much more concave in G. californicum , G. gnoma , and G. ridgwayi ); (3) edge of bone between tip of Proc. acrocoracoideus and Fac. artic. humeralis forms a fairly straight line, in posterior view (forms a moderately to deeply concave line in G. californicum , G. gnoma , and G. ridgwayi ); (4) distal rim of Fac. artic. sternalis, in sternal view, appears to have Angulus lateralis with less of a twist dorsad and overall less curvature, in ventral view, than in G. californicum , G. gnoma , and G. ridgwayi (the lesser twist is possibly a result of bone damage); and (5) Foramen n. supracoracoidei lies close to Cotyla scapularis, in dorsal view (lies farther away from Cotyla scapularis in G. californicum , G. gnoma , and G. ridgwayi (might be variable character, but it holds for specimens on hand).

The humerus of Glaucidium kurochkini ( Fig. 3) has some abrasion and breakage. It differs from that of G. californicum , G. gnoma , and G. ridgwayi by having (1) shaft with greater curvature in mid−length region, in posterior view; (2) Proc. flexorius, in posterior view, thicker dorsoventrally and not protruding as far distad as in G. californicum , G. gnoma , and G. ridgwayi ; and (3) Epicondylus dorsalis minimally protruding (minimally to moderately protruding in G. californicum and G. gnoma and significantly protruding in G. ridgwayi ). Damage to bone prevents identification of other distinguishing characters.

The radius of Glaucidium kurochkini differs from that of G. californicum , G. gnoma , and G. ridgwayi by having (1) Tuberculum bicipitale radii with distal end not protruding as distinctly from shaft distally; and (2) attachment for Lig. collaterale dorsale separated from that for Meniscus radioulnaris by distinct groove that lies at an angle to long axis of shaft (similar in G. ridgwayi ; groove minimal or absent in G. californicum and G. gnoma ).

The carpometacarpus of Glaucidium kurochkini ( Fig. 4 ) differs from that of G. californicum , G. gnoma , and G. ridgwayi by having (1) Fac. artic. alularis large (similar in G. ridgwayi ; smaller in G. californicum and G. gnoma ); (2) Os metacarpale alulare thick dorsoventrally (much thinner in G. californicum and G. gnoma ; intermediate in G. ridgwayi ); (3) Fovea carpalis anterior with very large foramen at bottom (very small to moderate−sized foramina in G. californicum , G. gnoma and G. ridgwayi ); (4) Trochlea carpalis broad (similar in G. ridgwayi ; narrower in G. californicum and G. gnoma ); (5) Spatium intermetacarpale with distal end a narrower “V”−shape rather than the broad “U”−shape seen in G. californicum , G. gnoma , and G. ridgwayi because the distal end of Os metacarpale minus does not curve posteriad just proximal to Synos. metacarpalis distalis, in ventral view; (6) Os metacarpale minus with proximal end wide (similar in G. ridgwayi , narrow in G. californicum and G. gnoma ); and (7) Fac. artic. digiti major with anterior projection more rounded, or less angular, in distal view, than in G. californicum , G. gnoma , and G. ridgwayi .

The femur of Glaucidium kurochkini ( Fig. 3) is somewhat abraded. It differs from that of G. californicum , G. gnoma and G. ridgwayi by having (1) Fovea lig. capitis very large and deep (not quite as large or deep in G. californicum and G. gnoma ; much smaller in G. ridgwayi ); (2) Caput femoris, in posterior view, not extending distad much beyond Collum femoris (extends significantly distad beyond Collum femoris in G. californicum and G. gnoma , and only slightly less so in G. ridgwayi ); (3) sulcus distal to posterolateral corner of Fac. artic. antitrochanterica weakly developed, although posterolateral corner of Fac. artic. antitrochanterica is slightly worn, reducing depth of sulcus (sulcus prominent in G. californicum and G. gnoma , slightly less prominent to weakly developed in G. ridgwayi ); (4) Condylus lateralis with abrupt, or almost 90 °, transition to shaft, in medial view (Condylus lateralis with posterior end undercut, in medial view, in G. californicum and G. gnoma ; not undercut and not transitioning quite as abruptly to shaft in G. ridgwayi ); (5) Condylus lateralis, in distal view, expanded mediad (similar in G. californicum and G. gnoma ; not expanded mediad in G. ridgwayi ); and (6) Condylus medialis not extending as far distad as Condylus lateralis (Condylus medialis extends farther distad in G. californicum , G. gnoma , and G. ridgwayi , but still not as far as Condylus lateralis).

The tibiotarsus of Glaucidium kurochkini ( Fig. 3) differs from that of G. californicum , G. gnoma , and G. ridgwayi by having (1) indentation between Fac. artic. medialis and Area interarticularis, in proximal view, less deep; (2) insertion for M. flexor cruris medialis a linear scar limited to anterior edge of Crista cnemialis (insertion scar with proximal end turning proximoposteriad for short distance in G. californicum and G. gnoma , and for a much greater distance in G. ridgwayi ; (3) Crista cnemialis anterior with medial side slightly concave (moderate to deep depression in G. californicum , G. gnoma , and G. ridgwayi ); and (4) shaft with anteromedial corner approaching Condylus medialis in a fairly straight line (shaft with anteromedial corner approaching Condylus medialis with a slight to moderate bowing mediad in G. californicum , G. gnoma , and G. ridgwayi ). Other than character (4), no distinctive distinguishing characters were observed for the distal end of the tibiotarsus of G. kurochkini , so the three specimens comprising incomplete distal ends can only be provisionally referred to G. kurochkini .

The holotypic tarsometatarsus of Glaucidium kurochkini has an extra distal foramen just proximal to the Incisura intertrochlearis medialis ( Fig. 1). A comparable foramen is not present in the referred tarsometatarsi from Carpinteria, nor in any of the modern comparative specimens. The unhttp://dx.doi.org/10.4202/app.2011.0125

usual occurrence of this foramen leads us to regard it as an anomaly rather than as a diagnostic character.

Remarks.—Worldwide, König and Weick (2008) recognize 25 species of pygmy owls in the genus Glaucidium and nine species in the genus Taenioglaux . Some of these species have vast ranges, but many have very restricted ranges, suggesting variations in geographic specificity. All pygmy owls are small, although some species are significantly larger or smaller than others, and some are more robust than the norm. The similarities in external morphology and plumage that led many species to be considered as races of polymorphic species are seen also in osteological characters, and those species that were formerly considered as members of a super−species complex are most similar. Although it is usually possible to identify sufficient characters to distinguish individual species, the number of individuals available as comparative osteological material for each species is limited. An additional problem is that in cases where multiple species have been considered together as a single, polymorphic species for many decades it is difficult to know whether certain skeletal specimens are assigned to the correct species, especially where geographic ranges overlap or when provenance data are generalized.

Using the method of Campbell and Bochenski (2010) for estimating the body mass of predatory birds, which was based on the work of Campbell and Marcus (1992), the mass of the individual represented by the single femur referred to Glaucidium kurochkini was calculated to be 71.4 g. This estimate is within the range of the body masses ( König and Weick 2008) of G. californicum (62–73 g), G. gnoma (48–73 g), and G. ridgwayi (46–102 g).

Of the specimens Howard (1962) tentatively referred to Glaucidium gnoma , four are presumably among the 12 specimens herein referred to G. kurochkini . The specimen from Pit 3, which was not identified as to element, could not be found in the collections. The eight newly identified specimens, including the holotypic tarsometatarsus, are all from the recently prepared material of Bliss 29.

Geographic and stratigraphic range.—Southern California, USA; upper Pleistocene.

Figures

Fig. 4. Stereopairs of specimens from late Pleis− tocene, Rancho La Brea, California, USA re− ferred to miniature owls Asphaltoglaux cecileae sp. nov. (A, C, D) and Glaucidium kurochkini sp. nov. (B). A. Left humerus (RLB K9441) in anterior (A1) and posterior (A2) views. B. Right carpometacarpus (RLB K9404) in dorsal (B1) and ventral (B2) views. C. Right femur (RLB K9349) in anterior (C1) and posterior (C2) views. D. Right coracoid (RLB E9533) in ven− tral (D1) and dorsal (D2) views. See Fig. 3 for additional labeled osteological features. Abbre− viations: artic., articularis; Fac., Facies.