Galligeranoides boriensis, Bourdon & Mourer-Chauviré & Laurent, 2016

Bourdon, Estelle, Mourer-Chauviré, Cécile & Laurent, Yves, 2016, Early Eocene birds from La Borie, southern France, Acta Palaeontologica Polonica 61 (1), pp. 175-190 : 182-187

Galligeranoides boriensis sp. nov.

Figs. 5A , 6 , 7 .

Etymology: From La Borie, the name of the quarry; in langue d’Oc language borie, large farm.

Type material: Holotype: MHNT.PAL.2013.16.3, distal part of left tibiotarsus ( Fig. 5A ) . Paratypes: MHNT.PAL.2013.16.1, right tibiotarsus ( Fig. 6A ) ; MHNT.PAL.2013.16.2, subcomplete right tarsometatarsus ( Fig. 6B ).

Type locality: La Borie, Saint-Papoul, Department of Aude , Southern France .

Type horizon: Middle Ypresian, early Eocene, close to reference level MP8–9 .

Diagnosis.—Tibiotarsus with condylus medialis projecting cranially and slightly deeper than condylus lateralis; cranial surface of distal end flat with a well-developed ridge along the medial side of this flat area; canalis extensorius located on the medial side and with two tiny openings; muscular tubercle located in the median axis of the bone and extended proximally by tuberositas retinaculi extensori; distinct groove between muscular tubercle and condylus lateralis; flattened surface on the lateral side of the tuberositas retinaculi extensori and proximal to condylus lateralis; trochlea cartilaginis tibialis bordered by bladelike projecting cristae trochleares.

Measurements (in mm).—MHNT.PAL.2013.16.3, distal part of left tibiotarsus (holotype): width of shaft on the cranial side, just proximal to the condyli, 16.9; depth of condylus medialis, 21.8; depth of condylus lateralis, 20.0; estimated distal width on the cranial side, 16.5; estimated width of trochlea cartilaginis tibialis, 13.7; width of condylus medialis on the cranial side, 6.5; width of condylus lateralis on the cranial side, 7.0. MHNT.PAL.2013.16.1, right tibiotarsus: total length (as preserved), 252.0; width at mid-shaft (as preserved), 12.3; depth at mid-shaft (as preserved), 9.8; width of shaft on the cranial side, just proximal to the condyli, 14.7; distal width (as preserved; condylus lateralis is incomplete), 16.0; depth of condylus medialis (as preserved; trochlea cartilaginis tibialis is incomplete), 17.0; width of condylus medialis on the cranial side, 6.5. MHNT.PAL.2013.16.2, right tarsometatarsus: total length (as preserved), 232.0; proximal depth from eminentia intercotylaris to cristae hypotarsi (as preserved), 21.5; depth of cotyla medialis, 12.0; depth at mid-shaft (as preserved), 11.4; width of sulcus flexorius at mid-shaft, 8.1; distal width, 24.7; distal depth, 16.1; width of trochlea metatarsi (TM) II, 6.0; depth of TM II (as preserved), 10.6; width of TM III, 11.0; depth of TM III, 11.2; width of TM IV, 7.1; depth of TM IV (as preserved), 11.0.

Description.— Tibiotarsi: The distal part of tibiotarsus MHNT.PAL.2013.16.3 (holotype) was found in site SP5. This left tibiotarsus is crushed and distorted. The cranial surface of the shaft is flat and shows a longitudinal ridge on its medial border. The openings of the canalis extensorius are very small and hardly visible. The pons supratendineus is very elongate in proximodistal direction. The muscular tubercle that is located at the distal part of the pons supratendineus is strongly projecting. It is situated in the median axis of the bone and is continuous with a strong crest which corresponds to the tuberositas retinaculi extensori. The tubercle is separated from the condylus lateralis by a deep groove. The condylus medialis is almost as wide as the condylus lateralis and the incisura intercondylaris is very narrow. The condylus medialis is strongly projecting cranially, partly because of distortion. It is, however, longer in craniocaudal direction than the condylus lateralis. The slight distal protrusion of the condylus medialis relative to the latter is due to crushing. The epicondylus medialis is well developed; the distal outline of the condylus is incompletely preserved but there is an indication of the presence of a notch. The trochlea cartilaginis tibialis is bounded on either side by strongly projecting, bladelike cristae trochleares. It is possible, however, that these cristae have been sharpened by crushing. The trochlea itself is narrow and deep. The distal outline of the condylus lateralis is flattened and shows no indentation. The epicondylus lateralis is weakly projecting. A flattened ligamentary insertion for the retinaculum musculi fibularis is located proximal to the condylus lateralis ( Fig. 7A ).

The tibiotarsus MHNT.PAL.2013.16.1 (also from site SP5) is broken and crushed. The proximal part is missing. The shaft is preserved up to the base of the crista cnemialis lateralis, but it is not possible to see the crista fibularis. The distal part lacks the trochlea cartilaginis cranialis and the cristae trochleares. The condylus lateralis and part of the shaft proximal to it are incompletely preserved. The preserved part of the distal end is similar to that of the holotype: the openings of the canalis extensorius are tiny; the pons supratendineus is proximodistally wide; the muscular tubercle is prolonged proximally by a crest located in the medial axis of the bone, and is separated from the condylus lateralis by a deep groove. The condylus medialis is relatively wide and strongly projected cranially, and the incisura intercondylaris is narrow.

Tarsometatarsus: The tarsometatarsus MHNT.PAL.2013. 16.2 (found in site SP2) is almost complete. The lateral part of the extremitas proximalis and part of TM IV are broken. The lateral rim of TM III is slightly eroded on the lateral and plantar sides. The wings of TM II and IV are also eroded. The proximal part and about 2/3 of the shaft are crushed in mediolateral direction. The eminentia intercotylaris is rounded and cranially projected, but rather flattened on the proximal articular surface. The cotyla medialis has a quadrangular outline. The fossa infracotylaris dorsalis is very deep and shows two foramina vascularia proximalia located almost at the same level. The preserved crista hypotarsi is plantarly prominent and rather medially directed. The rest of the hypotarsus is crushed but it is possible to see the trace of a canalis hypotarsi, which opened on the proximal articular surface, and extended distally over 3 cm ( Fig. 7B ). The sulcus extensorius is deep, but this character is strongly exaggerated by the crushing of the shaft. The sulcus extensorius extends over 4/5 of the shaft. The crista hypotarsi extends over a length of about 4 cm; the well developed cristae plantares extend over 4/5 of the shaft and border a wide, shallow sulcus flexorius. The distal part of TM III is wide, with two symmetrical rims. The distal part of TM IV reaches the mid-length of TM III, and TM II is slightly shorter than TM IV. In distal view the TM are disposed along a weakly curved line. TM II is slightly more plantarly displaced than TM IV. On the cranial face TM III is continued proximally as a wide, flattened, weakly projecting ridge. The foramen vasculare distale is very wide and opens at the distal end of a short groove. The incisurae intertrochleares are very wide, especially the lateral one. There is no indication of a fossa metatarsi I. The fossa supratrochlearis plantaris is wide and shallow. The opening of the canalis interosseus distalis is proximal to the incisura intertrochlearis lateralis and just distal to the opening of the foramen vasculare distale. TM III is not raised above the surface of the fossa supratrochlearis plantaris and ends proximally into a small circular depression.

Comparison with the Geranoididae .—The family Geranoididae includes five genera and seven species, mainly from the early Eocene of the Willwood Formation, and also from the middle Eocene of the Bridger Formation ( Cracraft 1969; Mayr 2009). So far it was known only from the West of the United States. These taxa are almost uniquely known by distal parts of tibiotarsi and by proximal and distal parts of tarsometatarsi. Their morphological characteristics were given by Cracraft (1969). The characteristics of the distal part of tibiotarsus are as follows: distal part not strongly elongated medially; distal outline of the condylus lateralis flattened (rounded in the genus Geranodornis ); distal outline of the condylus medialis showing a notch; condyli almost parallel to each other and incisura intercondylaris narrow; tubercle on the pons supratendineus moderately developed; condylus medialis not very cranially elongate and almost the same size as the condylus lateralis. On some of the tibiotarsi illustrated by Cracraft (1969), it is possible to see that the tubercle on pons supratendineus is extended proximally by a longitudinal ridge, and that this tubercle is separated from the condylus lateralis by a wide groove (e.g., in Geranoides jepseni , Eogeranoides campivagus , and Geranodornis aenigma ; Cracraft 1969: figs. 1, 6, and 10). Concerning Paragrus shufeldti, Cracraft (1969: 11) writes: “The tubercle is situated nearly in the middle of the bone, being offset slightly to the external side, and separated from the external condyle by a rather broad groove”. Also in Palaeophasianus meleagroides “there is a well-pronounced tubercle separated from the external condyle by a moderately broad groove” ( Cracraft 1969: 20).

The Galligeranoides tibiotarsi show the morphological characteristics of the Geranoididae , with some small differences. These differences are as follows: condylus medialis more craniocaudally elongate than condylus lateralis (almost equal in other Geranoididae ); openings of the canalis extensorius very narrow whereas they are generally wider in other Geranoididae (though they are very narrow in Geranodornis ); flattened surface between the tubercle and its extending crest and the lateral side of the shaft (in Geranoididae the tubercle and crest are generally closer to the lateral side); wide, deep groove between the tubercle and the condylus lateralis (shallower in other Geranoididae ); two projecting bladelike crests on the facies caudalis (less projecting in other Geranoididae ).

For the tarsometatarsus, the main characteristics indicated by Cracraft (1969) for the Geranoididae , which occur on La Borie tarsometatarsus, are as follows: eminentia intercotylaris relatively pointed and not broad; TM II and TM IV slightly plantarly displaced relative to TM III (TM II more than TM IV); incisurae intertrochleares relatively broad (lateral more so than medial). These features are present in Galligeranoides . The proximal part of the tarsometatarsus is known in Eogeranoides and Palaeophasianus , and the distal part in Paragrus and Palaeophasianus . In the two latter genera, TM IV reaches 2/3 of TM III whereas it is shorter in Galligeranoides and reaches only the mid-length of TM III. There is still, in these two genera, a larger difference in the relative lengths of TM II and IV.TM II is clearly shorter than TM IV whereas in Galligeranoides TM II is only slightly shorter than TM IV. Lastly, in the description of Geranoides jepseni Wetmore (1933: 115) writes: “facet for articulation of first toe small but evident”. In Galligeranoides this facet is not visible.

Comparison with the Eogruidae .—The Eogruidae are a family of large, long-legged birds which spanned from the middle Eocene to the early Pliocene of Eurasia ( Clarke et al. 2005; Mayr 2009). They are mainly known by distal parts of tibiotarsi and by tarsometatarsi. These tarsometatarsi are very elongate and show a projecting crest along the lateral border of their plantar surface. They are also characterized by the progressive reduction, then disappearance, of TM II over time ( Kurochkin 1976, 1981; Mayr 2009).

The distal part of tibiotarsus MHNT.PAL.2013.16.3 is very different from the tibiotarsi of the genus Eogrus (see Wetmore 1934: fig. 4; Cracraft 1973b: fig. 47; Clarke et al. 2005: fig. 8). On the paratype tibiotarsus of Eogrus aeola Wetmore 1934 : fig. 4), the canalis extensorius has two wide openings and is situated close to the middle of the facies cranialis. The pons supratendineus is proximodistally short. The muscular tubercle is weakly developed. Both condyli are almost the same depth in craniocaudal direction and almost the same width on the facies cranialis. The tibiotarsus of Eogrus wetmorei Brodkorb, 1967 , from the Miocene of China, figured in Clarke et al. (2005: fig. 8A) shows the same characteristics.

On the tarsometatarsus of Eogrus aeola , the three trochleae are arranged on a weakly curved line, but TM II is much narrower than TM IV, whereas in Galligeranoides they have nearly the same width. In addition, TM II is much shorter than TM IV and hardly reaches 1/3 of TM III length. TM II is still shorter on the tarsometatarsus AMNH 2937. These characteristics are conspicuous on the tarsometatarsi figured in Clarke et al. (2005: figs. 2, 3, 5, 6). The tarsometatarsi of Eogruidae are also characterized by the presence of a plantarly projecting crest, on the facies plantaris of the shaft, on the lateral side ( Kurochkin 1981: fig. 10; Mayr 2009). In Galligeranoides , the crista plantaris lateralis is not more projected than the crista plantaris medialis, but the shaft has been mediolaterally compressed.

Comparison with the Parvigruidae .—This family is based on the taxon Parvigrus pohli Mayr, 2005 , from the Early Oligocene of Luberon, France. In Parvigrus , the distal part of the tarsometatarsus looks similar to those of Aramidae and Balearica . Its TM II is plantarly displaced and is shorter than TM III, but it is not as short as in the Gruidae . Rupelrallus saxoniensis Fischer, 1997 , from the Early Oligocene of Weisselsterbeckens near Leipzig, Germany, was described as a Rallidae but, according to Mayr (2006, 2009, 2013) it can be attributed to the family Parvigruidae . The tibiotarsi and tarsometatarsus of Galligeranoides differ from this taxon because in Rupelrallus the tibiotarsus lacks a tubercle at the pons supratendineus, the condylus lateralis is very elongate in proximal direction along the craniolateral angle, and the trochlea cartilaginis tibialis is narrow. In Rupelrallus , the tarsometatarsus has a very short and strongly plantarly displaced TM II (see Fischer 1997: figs. 13a, b, 15a, b).

Comparison with the Gruidae .—The extant family Gruidae appeared in the middle Eocene with the genus Palaeogrus . In the Gruidae , on the distal part of the tibiotarsus, in distal view, the condylus medialis is parallel to the condylus lateralis, and then shows a discontinuity in alignment ( Fig. 7C ). This morphological characteristic is very slightly visible also in Psophia , but not in Aramus .

Palaeogrus princeps Portis, 1884 is known by a distal part of left tibiotarsus from the Lutetian of Italy ( Portis 1884: pl. 1: 1–4). On the facies cranialis, it is only possible to see the wide proximal opening of the canalis extensorius, located almost in the middle of the cranial surface, but other morphological details are not visible “because the rest is masked by the still adherent sediments” ( Portis 1884: 363, our translation from Italian). The lateral, caudal, and distal views of this tibiotarsus show the characteristic shape of the Gruidae , with the medial shift of the condylus medialis.

Palaeogrus hordwelliensis (Lydekker, 1891) , from the late Eocene of England, is also known by a distal part of right tibiotarsus. Palaeogrus excelsa (Milne-Edwards, 1871) from the early and middle Miocene of France ( Cheneval 2000; Mlíkovský 2002) is known by a large number of elements of the postcranial skeleton. Palaeogrus mainburgensis Göhlich, 2003 , from the middle Miocene of Germany is also known by several elements including a distal part of tibiotarsus ( Göhlich 2003). In these three species, the distal tibiotarsus shows the characteristics of the Gruidae : wide openings of the canalis extensorius; presence of a tubercle on the laterodistal border of the pons supratendineus; cranial end of condylus medialis thin; condylus medialis craniocaudally longer than condylus lateralis and showing a medial shift in distal view. In Palaeogrus excelsa , the distal part of the tarsometatarsus (visible on the specimen MHNL St.G. 64) shows that TM II is very short and strongly plantarly displaced. In this respect, P. excelsa is more similar to the Recent genus Grus than to the Recent genus Balearica . The species Palaeogrus geiseltalensis Lambrecht, 1935 , from the middle Eocene of Geiseltal, has been placed in synonymy with Palaeotis weigelti Lambrecht, 1928 by Houde and Haubold (1987). These authors assign the genus Palaeotis to the Struthionidae .

The extinct genus Geranopsis was described from the late Eocene of England. It included two species, Geranopsis hastingsiae Lydekker, 1891 , and Geranopsis elatus Milne-Edwards, 1892 , from the Eocene or Oligocene of the Phosphorites du Quercy, in France. Geranopsis elatus has been transferred to the genus Occitaniavis and to the family Idiornithidae , suborder Cariamae ( Mourer-Chauviré 1983) . The holotype of G. hastingsiae is a left coracoideum which has been placed in the Gruidae probably because of the presence of a large pneumatic fossa on the dorsal surface, just proximal to the facies articularis sternalis ( Cracraft 1973b; Harrison and Walker 1976). Later, Harrison and Walker tentatively referred to this species an omal part of coracoideum, three distal ends of tibiotarsi, and a proximal part of tarsometatarsus from the early Oligocene of England ( Harrison and Walker 1979). Mayr (2005: 523 and 2009: 51, 103) remarked that the coracoideum of G. hastingsiae is morphologically very similar to the coracoideum of Anserpica kiliani Mourer-Chauviré, Berthet, and Hugueney, 2004 , from the late Oligocene of France, which has been attributed to the Anseranatidae ( Mourer-Chauviré et al. 2004) . The coracoideum of Geranopsis differs from the Gruidae because its omal part is much shorter, compared to its total length, than in the latter taxon. In Gruidae the length of the omal part (from the top of processus acrocoracoideus to the sternal bor- der of the cotyla scapularis) corresponds to about half of the internal length (from the top of processus acrocoracoideus to the angulus medialis of the facies articularis sternalis), while in Geranopsis the omal part is less developed and corresponds to about 30% of the internal length. In our opinion, the holotype coracoideum of G. hastingsiae probably does not belong to the Gruidae , and other elements referred to this species should be revised. The distal parts of tibiotarsi differ from Galligeranoides because they are wider than deep in distal view, and because both condyli are weakly projecting cranially. In addition, they are much smaller in size.

Stratigraphic and geographic range.—Ypresian (early Eocene), southern France.

Figures

Fig. 5. Limb bones of early Eocene birds, La Borie, France. A. Geranoidid Galligeranoides boriensis gen. et sp. nov., left tibiotarsus, MHNT. PAL.2013.16.3 (holotype), in cranial (A 1), caudal (A2), distal (A3), lateral (A4), and medial (A5) views. B. Undetermined bird, left ulna, MHNT. PAL.2013.16.4, in dorsal (B1), ventral (B2), proximal part in ventral (B3) and distal part in ventral (B4) views.

Fig. 6. Geranoidid bird Galligeranoides boriensis gen. et sp. nov., early Eocene, La Borie, France. A. Right tibiotarsus MHNT.PAL.2013.16.1 (paratype), in cranial (A1) and caudal (A2) views and distal part in cranial view (A3). B. Right tarsometatarsus MHNT.PAL.2013.16.2 (paratype), in cra- nial (B1), plantar (B2), proximal (B3), and distal (B4) views.

Fig. 7. Diagrams of limb bones of geranoidid bird Galligeranoides boriensis gen. et sp. nov., early Eocene, La Borie, France (A, B) and Grus grus (Linnaeus, 1758), extant, Eurasia and Africa (C). A. Distal part, cranial view of left tibiotarsus MHNT.PAL.2013.16.3. B. Proximal part, medial view of right tarsometatarsus MHNT.PAL.2013.16.2. C. Distal end of left tibiotarsus, showing the discontinuity in alignment of the condylus medialis.