SYTEMATIC PALEONTOLOGY
CLASS AVES
Order Galliformes
Family Phasianidae Horsfield, 1821
Tribe Tetraonini Leach, 1820
Genus
Paralyra Zelenkov, gen. nov.
Etymology. From Greek para (next to) and lyra (a lyre), a reference to the generic name of Lyrurus black grouse; feminine.
Typespecies. Lagopus atavus Jánossy, 1974; Pliocene–Lower Pleistocene of Central and Eastern Europe
Diagnosis. The shaft of the tarsometatarsus is noticeably widened, only slightly narrowing in the central part; the medial edge of the cotyla medialis is slightly curved proximally; fossa parahypotarsalis
medialis is small, with its dorsal edge extending proximally,
obliquely to the long axis of the bone, and ending almost at the level of the dorsal edge of the shaft; crista hypotarsalis medialis is ending at the same level as the crista hypotarsalis lateralis and abruptly terminates distally; the proximolateral part of the dorsal surface of the shaft immediately distal to the cotyla lateralis forms a flat surface; trochlea metatarsi IV is extended distally (its distal edge is close to the distal edge of trochlea metatarsi III) and slightly set back laterally (its proximolateral edge gently passes to the shaft); trochlea metatarsi III does not form a pointed proximal “lip” in plantar view; foramen vasculare distale is close to incisura intertrochlearis lateralis on the plantar surface.
Species composition. Type species.
Comparison (Fig. 1). The tarsometatarsus differs from that of
Lagopus in an expanded shaft; a proximally weakly curved medial edge of the cotyla medialis; the dorsal edge of the fossa parahypotarsalis medialis, almost reaching the dorsal edge of the shaft; the flattened dorsal surface of the shaft immediately distal to the cotyla lateralis; trochlea metatarsi IV slightly set back laterally (Fig. 1, s1) and strongly extended distally (Fig. 1, g1); and the absence of a pointed “lip” in the proximal part of the plantar surface of trochlea metatarsi III (this feature varies in
Lagopus). It differs from
Lyrurus in the greater robustness of the proximal end and trochlea metatarsi IV slightly set back laterally with respect to the shaft and extended distally (as in
Lagopus, the transition of the
lateral edge of the shaft to trochlea metatarsi IV is sharper in
Lyrurus, while the trochlea itself is positioned more proximally), and subquadrate trochlea metatarsi III in distal view (rectangular and dorsoventrally high in
Lyrurus), as well as in the plantar aperture of the foramen vascularis distalis, which is close to the incisura intertrochlearis lateralis.
Remarks. A small grouse,
Lagopus atavus, was described from the Upper Pliocene of southern Poland (Jánossy, 1974) as a fossil subspecies of the modern willow grouse
L. lagopus (L., 1758), then
raised to the species rank (Jánossy, 1976), and then again included in the synonyms of modern
L. lagopus (Mlíkovský, 2002). The assignment of this species to the genus
Lagopus (ptarmigans) is largely based on its size (larger than
Tetrastes and smaller than
Lyrurus). At the same time, it is in many cases problematic to distinguish the genera Lagopus and
Lyrurus by postcranial osteology: I did not find unambiguous criteria for differentiating these genera (except the size), which could be traced in the described materials of
L. atavus. Modern
Lyrurus mlokosiewiczi does not significantly differ from the largest representatives of
Lagopus in the size of the forelimb bones (however, it has a noticeably longer tarsometatarsus) and it seems completely unjustified to rely on the size parameter when determining the generic attribution of fossil Plio-Pleistocene representatives of the lineage. It is also important that the type series of
L. atavus is characterized by limb
proportions differing from those in the modern representatives
of
Lagopus (Bocheński, 1991).
The humerus of
L. atavus, which is the holotype of this species, is characterized by the presence of a g ove in the site of the imprint of m. latissimus dorsis posterior (Jánossy, 1974); however, I also found a similar groove in Lyrurus mlokosiewiczi, while it is usually indistinct in
Lagopus (Bocheński, 1991; our data). The concavity on the proximal surface of the tuberculum ventrale in
L. atavus (Jánossy, 1974) is also present in black grouse as an individual variation; however, it is more developed in Lagopus (if present); this character can be considered the only feature that brings this fossil species closer to the genus
Lagopus.
However, the most remarkable is the structure of the tarsometatarsus of
L. atavus:
Lagopus and
Lyrurus as well as other grouse genera, are clearly distinguishable by this skeletal element (Fig. 1). Only one distal fragment was previously known; the researchers did not make any meaningful comments about it (Fig. 1c). The complete tarsometatarsus from the Taurida Cave (see the species identification of this specimen below) indicates a clearly defined morphological specificity of
L. atavus compared to modern representatives of
Lagopus. The tarsometatarsus of
L. atavus differs from that in modern
Lagopus species in a distinctly thickened shaft, as well as in trochlea metatarsi IV noticeably extended distally and somewhat less offset laterally. With respect to the size of the proximal articular surface, the tarsometatarsus of
L. atavus corresponds to that of
L. lagopus; however, it is significantly
shorter.
Despite the relatively small size, the structure of the tarsometatarsus brings
L. atavus closer to modern
Lyrurus. Therefore, the assignment of
L. atavus to the genus
Lagopus seems unjustified. Taking into account the uncertainty of the phylogenetic relationship of
L. atavus with the modern genera
Lagopus and
Lyrurus and the specificity of the tarsometatarsus structure, a separate generic status is accepted for this species here. ifferences from the modern species of
Lagopus in the structure of the distal articular surface (a pronouncedly distally extended and laterally less offset trochlea metatarsi IV), indicate different patterns of interaction with the substrate between the Villafranchian
Paralyra atavus (Jánossy, 1976) comb. nov., which lived in savanna or steppe landscapes, and modern
Lagopus species, which generally inhabit the subarctic.
The tarsometatarsus of
Paralyra is similar in general proportions to that of North American
Dendragapus obscurus (Fig. 1f), but differs from it in wide and low trochlea metatarsi III in distal view. As in
Lagopus, trochlea metatarsi IV has a well-defined, albeit shallow,
groove on the distal and dorsal sides of the block, while this groove in
Dendragapus disappears in the middle part of the trochlea. Species of the genus
Falcipennis have a narrowed tarsometatarsal shaft with an expanded distal end, which makes them similar to
Lagopus, but differentiates them from
Dendragapus and
Paralyra. The tarsometatarsus of
Paralyra differs from
Tympanuchus in dorsoplantarly low trochlea metatarsi III and dorsally located trochlea metatarsi IV in distal view and a plantar foramen vasculare distale closely located to incisura intertrochlearis lateralis, as well as in the absence of a distinct proximal “lip” on the lateral edge of trochlea metatarsi III in plantar view and a less developed fossa parahypotarsalis lateralis. Therefore, despite the proportional similarity with
Dendragapus,
Paralyra is closer to
Lagopus and
Lyrurus with respect to the structure of the metatarsophalangeal
joints. The assignment of
P. atavus to the evolutionary lineage of black grouse and ptarmigans is also indirectly confirmed by the absence of representatives of taiga faunas (which include
Dendragapus) in the vertebrate complex of Taurida, which is characterized by a savanna–forest-steppe ecological appearance (Lopatin, 2019).
The coracoid from the Rębielice Królewskie 1 locality, assigned to
L. atavus (Jánossy, 1974), confirms the separate generic status of this form (Fig. 1). Specimen ISEZ, no. AF/16-RK1:12 (cranial fragment of the left coracoid) is similar to Lagopus in the shape of facies articularis clavicularis, but noticeably differs from it in a shorter but not medially extended processus acrocoracoideus (with respect to the latter feature, it is more similar to
Lyrurus).
Reconsideration of the taxonomic position of Pliocene
L. atavus requires a revision of other supposed finds of ptarmigans in the Pliocene of Eastern Europe. Thus, L
agopus aff.
L. atavus was identified based mainly on dimensions using a very fragmentary humerus from the Early Pliocene of the Muselievo locality in Bulgaria (Boev, 2001). The structure of the preserved part of the bone makes it hardly possible to identify closely related grouse genera; however, based on the size similarity and age, this specimen can tentatively be designated as
Paralyra sp.
As noted by Bocheński (1991), the tibiotarsus of
Lagopus from Weże demonstrates an intermediate morphology between modern
Lagopus and
Lyrurus, thereby supporting a separate generic status for Pliocene–Early Pleistocene East European ptarmigans. The assignment of this find to ptarmigans (as P
aralyra sp.) is confirmed here.
Paralyra atavus (Jánossy, 1974), comb. nov.
Lagopus lagopus atavus: Jánossy, 1974, p. 534, pl. 24
Lagopus avatus: Jánossy, 1976, p. 33; Bocheński, 1991, p. 570;
Bocheński et al., 2012, p. 58.
Lagopus lagopus (part.): Mlíkovský, 2002, p. 168.
Holotype. ISEZ, no. AF/26-RK1:22, proximal fragment of the humerus; Poland, Rębielice Królewskie 1 locality; Upper Pliocene.
Description (Figs. 1b, 1d, 1l, 1g, 1i, 1j, 1o, 1p). See the diagnosis of the genus and the original description of the species in (Jánossy, 1974).
Measurements, in mm. Tarsometatarsus: total length, 36.5; width of the proximal end, 8.1; minimum width of the shaft, 3.6; height of the shaft in the middle part, 2.8; width of the distal end, 8.3; height of trochlea metatarsi III, 4.2. Tibiotarsus: width of the distal end, about 7.7.
Remarks. Tarsometatarsus from the Taurida Cave (specimen PIN, no. 5644/233) is characterized by general shortening, which significantly distinguishes it from the vast majority of representatives of Phasianidae, including
Alectoris, with which it is similar in the size of the articular surfaces. This specimen also differs from
Alectoris (the proportionally closest non-grouse Phasianidae) by the following features: trochlea metatarsi III has a strongly convex dorsal surface and projects cranially in medial and lateral views (Fig. 1q; Bogdanovich, 1997, p. 27); the dorsal edge of trochlea metatarsi IV is turned outward (laterally), which involves the lateral expansion of incisura intertrochlearis lateralis (Fig. 1, iil); fossa parahypotarsalis lateralis does not expand dorsally in lateral view (its dorsal edge is subparallel to the long axis of the bone):
the tarsometatarsus from Taurida is similar to that of Tetraonini in these features. In
Alectoris, the trochlea metatarsi III is on a level with the dorsal edge of the shaft; trochlea metatarsi IV is not turned outward (incisura intertrochlearis lateralis has an even width in distal view); fossa parahypotarsalis lateralis clearly expands dorsally in lateral view (its dorsal edge is oblique).
The specimen from Taurida corresponds in size to the smallest
L. lagopus or largest
L. muta (see Stewart, 2007) and is thus comparable to the fossil
L. atavus known from the Late Pliocene–Early Pleistocene (MN 16–MN 17) of Poland and, presumably, Early
Pliocene of Bulgaria (Jánossy, 1974; Bocheński, 1991; Boev, 2001, 2002; Bocheński et al., 2012). Complete tarsometatarsi were not described for L. atavus; therefore,the proportions of the tarsometatarsus remained unknown for this species. At the same time, the fragmentary distal tarsometatarsus from Rembelice Królewski 1, assigned to L. atavus (see Jánossy, 1974), is similar to specimen PIN, no. 5644/233 in trochlea metatarsi IV slightly deviating laterally and strongly extended distally, as well as in a thickened (widened) shaft, judging from the preserved fragment. This (in particular, the unusual morphology of trochlea metatarsi IV for grouse) makes it possible to assign specimen PIN, no. 5644/233 to
L. atavus.
The distal fragment of the tibiotarsus (specimen PIN, no. 5644/232) is similar in absolute size to that of
L. lagopus and Alectoris graeca and also corresponds in size to the articular part of the distal tarsometatarsus of specimen PIN, no. 5644/233. Tibiotarsus from the Taurida Cave (specimen PIN, no. 5644/232) is similar to that of
Lagopus and differs from
Alectoris in the following features: pons supratendineus is narrow and oriented at a slight angle to the long axis of the bone (in
Alectoris, it is noticeably wider and obliquely oriented); the distal aperture of canalis extensorius is largely oriented subperpendicular to the long axis of the bone (obliquely in
Alectoris; related to the previously mentioned feature); canalis extensorius and pons supratendineus are close to the lateral edge of the bone (to the medial edge in
Alectoris); condylus lateralis
slightly protrudes distally relative to the condylus medialis in cranial and caudal views (in
Alectoris, the lateral condyle protrudes significantly more distally than the medial one, which makes the distal edge of the tibiotarsus markedly asymmetrical); incisura intercondylaris is rather wide (wider than each of the condyles) in distal view (narrow in Alectoris; narrower than the condyles). Specimen PIN, no. 5644/232 also differs in all these features from
P. perdix, which also has smaller dimensions. A very characteristic feature of the described specimen is the presence of an elongated
tendon scar (apophysis externum ligamenti obliqui), located on the lateral edge of the pons supratendineus and separated from condylus lateralis with a flat area (Fig. 1, fa), as in
Lagopus and
Lyrurus. In
Alectoris,
Perdix, and other phasianids, this scar is uberous in shape and close to or merges with the condylus lateralis. Specimen PIN, no. 5644/232 is similar in absolute size to the tibiotarsus of “
Francolinus”
capeki Lambrecht, 1933, from which it differs in the above-mentioned scar morphology, as well as in a craniocaudal narrow end in distal view and in a cranially low condylus lateralis.
The tibiotarsus from the Taurida Cave (specimen PIN, no. 5644/232) differs from that of
P. atavus from the type locality in some craniocaudal shortening in distal view, as well as in a more distant muscular imprint on the lateral part of the pons supratendineus
from the proximal edge of this bridge (in P. atavus from Rembelice Królewski 1, it is closer to this edge). With respect to the structure of sulcus intercondylaris, specimen PIN, no. 5644/232 is close to P. atavus from Poland and modern Lagopus muta, which have a pronounced bend in the transition zone from sulcus to condylus lateralis;
L. lagopus has no bend in this area and the sulcus intercondylaris smoothly passes to the lateral condyle in cranial view. It is quite possible that the form from the Taurida Cave may represent a separate species; however, the poor preservation of all
known tibiotarsi of
P. atavus (including the described specimen) prevents conclusions about a separate species status for the Crimean form.
Occurrence. Upper Pliocene–Lower Pleistocene of Poland (Bocheński, 1991; Bocheński et al., 2012) and Lower Pleistocene of Crimea
Material. Specimen PIN, nos. 5644/1522, cranial fragment of the sternum; 5644/232, distal fragment of the left tibiotarsus; 5644/233, right tarsometatarsus; Taurida Cave, Crimea; Lower Pleistocene.
Fred
Fig. 1. Tarsometatarsus ((a)–
), tibiotarsus (o), and coracoids ((p), (q)) of Paralyra atavus (Jánossy, 1974) from the Upper Pliocene–
Lower Pleistocene of Eastern Europe in comparison with selected modern Tetraonini: (a), (k), (q)
Lagopus lagopus (L., 1758), specimen PIN 47-4-3 from the osteological collection, modern; (b)–(d), (g), (i), (j), (l), (o), (p)
Paralyra atavus: (b), (d), (g), (i), (j), (l) specimen PIN, no. 5644/233, Crimea, Taurida Cave; Lower Pleistocene; (c) specimen b/n from the ISEZ collection (Jánossy, 1974), Poland, Rębielice Królewskie 1; Upper Pliocene; (o) specimen PIN, no. 5644/232, Crimea, Taurida Cave; Lower Pleistocene; (p) specimen ISEZ, no. AF/16-RK1:12, Poland, Rębielice Królewskie 1; Upper Pliocene;
(e), (h), (m) Lyrurus tetrix (L., 1758), specimen PIN 47-8-2 from the osteological collection, modern; (f),
Dendragapus obscurus (Say, 1823), specimen PIN 47-3-1 from the osteological collection, modern. (a), (c)–(f) dorsal view; (b) proximal view; (g), (h) plantar view; (i) medial view; (j) lateral view; (k)–
distal view; (o) cranial view; (p), (q) ventral view. Designations: c, cranially projecting trochlea metatarsi III, in medial view; cl, cotyla lateralis; col, condylus lateralis; fa, a facet separating the tendon scar from the condylus lateralis; fpl, fossa parahypotarsalis lateralis; fpm, fossa parahypotarsalis medialis; fvd, foramen vasculare distale; g1, trochlea metatarsi IV poorly advanced distally, close to trochlea metatarsi III; g2, trochlea metatarsi IV poorly advanced distally, distant from trochlea metatarsi III; iil, incisura intertrochlearis lateralis; mcm, medial edge of cotyla medialis; pa, processus acrocoracoideus; sc, tendon scar (apophysis externum ligamenti obliqui); s1, trochlea metatarsi IV slightly set back laterally (gradually expanding) in Paralyra atavus; s2, trochlea metatarsi IV sharply (strongly) set back laterally; tm II–IV, trochleae metatarsorum II–IV. Scale bar 10 mm.
