Qiliania undetermined
|
publication ID |
https://doi.org/ 10.1111/j.1096-3642.2010.00671.x |
|
persistent identifier |
https://treatment.plazi.org/id/5D0287F1-FF81-004B-86AD-FB7FFEF7FB19 |
|
treatment provided by |
Carolina |
|
scientific name |
Qiliania undetermined |
| status |
SP. |
Holotype: FRDC-05 -CM-006, a nearly complete left pelvic girdle and limb, lacking only the preacetabular portion of the ilium and the femoral head. The specimen is completely articulated save for the pelvic girdle and femur, which have been slightly displaced ( Fig. 2 View Figure 2 ).
Type horizon: Xiagou Formation, Lower Cretaceous [Aptian ( Li & Yang, 2004; You et al., 2006; Suarez et al., 2008)].
Type locality: Near the town of Changma, in the Changma Basin of Gansu Province, north-western China. Precise locality information is available to qualified researchers upon request.
Referred material: FRDC- 04-CM-006, a partial right pelvic limb consisting of the femur missing its proximal end, the complete tibiotarsus, and the tarsometatarsus lacking its distal end ( Figs 3 View Figure 3 , 4 View Figure 4 ). Upon discovery, the specimen was partially articulated, but it has since been disarticulated and prepared free of matrix to facilitate study.
Etymology: In honour of Dr Gregory Graffin, lecturer at the University of California, Los Angeles and co-founder of the musical group Bad Religion, for his contributions to evolutionary biology, his public outreach through music, and his inspiration to young scientists around the world.
Diagnosis: Qiliania graffini is distinguished from other presently known enantiornithines by its possession of the following autapomorphies: distal quarter of pubis deflected ventrally; tibiotarsus very long and slender, with mid-shaft mediolateral width to proximodistal length ratio of less than 0.05 and proximodistal length 133% that of femur; tibiotarsus with craniocaudally elongate and subrectangular proximal articular surface, well-developed cnemial crest, and deep distolateral fossa; and tarsometatarsus very long and slender (63% of proximodistal length of tibiotarsus). The taxon is further diagnosed by the following unique combination of apomorphies that occur, individually or in subsets, in other enantiorni- thine taxa: deeply excavated medial epicondylar depression and shallower lateral epicondylar depression on the distal tibiotarsus; distinct fibula fully fused to tibiotarsus; plantarily excavated tarsometatarsus; pedal unguals and associated keratinous sheaths relatively straight; and pedal ungual IV reduced (see Comparisons).
DESCRIPTION
GENERAL
Specimen FRDC-04-CM-006 has been prepared entirely free of matrix (and, notably, is one of the very few Early Cretaceous enantiornithine specimens that is currently in such a condition); specimen FRDC-05- CM-006 remains articulated and embedded in matrix, with the pelvic limb exposed in medial view and the pelvic girdle in lateral view. The complete fusion of the proximal tarsals to the tibia in both specimens indicates that they probably pertain to adult individuals. demarcated by the prominent dorsal process of the ischium. The dorsal process contacts the ilium ventromedially but remains unfused. The ilioischiadic foramen is subtriangular in outline, with a craniocaudal diameter of 2.24 mm and a dorsoventral diameter of 1.78 mm. It is thus considerably smaller than the acetabulum, the lateral margin of which has a roughly uniform diameter of 2.36 mm.
Distal to the dorsal process, the ischium is knifelike, narrowing slightly in craniocaudal dimension distally and lacking an obturator process. The distalmost tip of the ischium is abraded, but it seems unlikely that the bone extended much farther. The distal one-fifth of the ischium is deflected slightly dorsally. There also appears to have been a laterally projecting crest on the ischium that has been obscured by crushing.
The very thin, long, rod-shaped pubis terminates in a small tubercle rather than a distinct boot. Most of the shaft of the pubis is orientated parallel to that of the ischium; however, the distal-most portion of the former is gently ventrally deflected. The pubis is not mediolaterally compressed.
Their small sizes are therefore probably not ontogenetic artefacts.
PELVIC GIRDLE
Specimen FRDC-05-CM-006 preserves a nearly complete left pelvic girdle that lacks only the preacetabular portion of the ilium ( Fig. 2 View Figure 2 ). The pelvic girdle elements are fully fused. The postacetabular wing of the ilium is subtriangular in lateral view, tapering caudally, and is gently excavated throughout its length, forming a shallow lateral concavity that is bordered dorsally by a straight and delicate dorsal iliac crest. The presence of a laterally projecting supraacetabular tubercle is ambiguous because of the breakage of the cranial portion of the ilium.
A crest circumscribes the margin of the acetabulum, forming a distinct lip. The caudodorsal rim of this lip tapers into a very prominent, strongly laterally projecting antitrochanter. The lateral acetabular opening is greater in diameter than its medial counterpart. The pubic and ischial peduncles of the ilium cannot be clearly distinguished from the proximal extremes of the pubis and ischium, respectively. Caudal to the antitrochanter, the ilioischiadic foramen is caudally
FEMUR
Femora are nearly completely preserved and broken at essentially identical points along the distal shaft in both specimens. The femur of FRDC-05-CM-006 lacks only the head, which has been broken off the small yet distinct femoral neck ( Fig. 2 View Figure 2 ); that of FRDC-04- CM-006 is missing the entire proximal end. The caudolateral margin of the proximal femur bears a distinct caudal (=‘posterior’) trochanter, an enantiornithine apomorphy ( Chiappe & Walker, 2002). The trochanter angles caudolaterally, away from the head of the femur. The femoral shaft is bowed in the cranial direction, most strongly so distally.
As observed in caudal view, the prominent popliteal fossa extends nearly to midshaft. Distally, this fossa continues as a shallow groove between the two condyles. The distal ends of the femora of both specimens have been crushed caudomedially, rendering the condyles unusually angular and distorting the morphology of the end of the bone. The lateral and medial condyles are prominent in caudal view, subrectangular in shape, and subequal in size. A weakly developed fibular trochlea appears to be present. The distolateral margin of the femur lacks the caudal projection present in some enantiornithines (e.g. PVL 4037; Chiappe & Walker, 2002). A prominent lateral epicondyle is visible on the femur of FRDC-04-CM-006, and is fully distinct from the lateral condyle.
TIBIOTARSUS AND FIBULA
The tibiotarsus of FRDC-05-CM-006 is complete, essentially undamaged, and mainly exposed in medial view, with some cranial and caudal morphologies also discernable ( Fig. 2 View Figure 2 ). The FRDC-04-CM-006 tibiotarsus is also complete, but appears to have been diagenetically distorted to a degree that is difficult to ascertain ( Fig. 3 View Figure 3 ). The tibia and proximal tarsals are fully fused, forming a true tibiotarsus. The proximal half of the shaft is widest craniocaudally, whereas the distal portion is broadest mediolaterally. The tibiotarsus of Qiliania is long and slender, with a midshaft width to element length ratio of 23:1, and a femoral to tibiotarsal length ratio of 3:4 ( Table 1).
The proximal articular surface of the tibiotarsus is subrectangular in contour and orientated perpendicular to the shaft. Laterally, in FRDC-04-CM-006, the undamaged fibula is articulated with, and fully fused to, the tibiotarsus. Cranial to the fibula lies a pronounced fibular crest that appears to have been slightly crushed cranially. The fibular crest is relatively short, extending distally approximately 8 mm (about one-quarter of the total length of the tibiotar- sus) and ending in a cranially projecting tubercle for the insertion of the M. iliofibularis. The fibula is longer, measuring 13.4 mm in length, but it tapers sharply, becoming narrow and splint-like distal to the fibular crest. There is a well-developed cnemial crest on the craniomedial surface of the proximal tibiotarsus of FRDC-04-CM-006; because the cnemial crest of enantiornithines is typically low and poorly developed, Q. graffini is unusual in this respect. Medially, there is a deep sulcus on the proximal end of the tibiotarsal shaft. Although this structure may have been exaggerated by crushing, its presence in both specimens suggests that it is a true feature of this taxon.
Proximal to the distal condyles, on the craniomedial margin of the tibiotarsus, a tubercle medially demarcates a shallow groove that is laterally bordered by the raised ascending process of the astragalus. This is interpreted as the sulcus for the tendon of the M. extensor digitorum longus and the M. tibialis crania- lis, with the craniomedial tubercle and the ascending process representing the insertions for the extensor retinaculum. The former of these hypothesized insertion sites lies proximal to the latter; this proximodistal ‘staggering’ lends support to our interpretation of these areas as extensor retinaculum insertion sites because this retinaculum is orientated obliquely in modern birds (Baumel & Witmer, 1993) and possibly also the Cretaceous ornithuromorph Apsaravis ukhaana ( Clarke & Norell, 2002) . The astragalar ascending process is expressed in relief on the cranial margin of the tibiotarsus and is therefore visible in mediolateral view. Distally, in caudal view, the synostosis marking the fusion of the astragalus to the tibia is also faintly visible. In FRDC-04-CM-006, the distalmost portion of the tibiotarsus abruptly expands mediolaterally to nearly twice the width of the shaft.
The medial and lateral distal condyles are prominent in cranial view. The medial condyle is slightly wider mediolaterally and deeper proximodistally than its lateral counterpart, although this difference is subtle. The intercondylar sulcus is present but shallow, and is orientated slightly proximolaterally– distomedially, oblique to the long axis of the tibiotarsal shaft. Because this sulcus is shallow, the distal condyles taper smoothly toward each other, forming an hourglass shape in craniodistal view. The medial surface of the medial condyle is deeply excavated by a circular epicondylar depression. In the FRDC-04-CM- 006 tibiotarsus, the lateral surface of the lateral condyle is embayed by a shallower lateral epicondylar depression. As on the medial side, this depression is bordered caudally by an epicondyle; the lateral side, however, bears an additional excavation – much deeper than either of the epicondylar depressions and otherwise unknown within enantiornithines – slightly proximocaudal to the epicondyle. This lateral depression is bordered by a raised, rugose area formed by the fusion of the proximal tarsals and the tibia that is continuous with the lateral margin of the ascending process. The placement of these structures suggests that they are functionally analogous to the M. fibularis sulcus and retinacular tubercle of modern birds, respectively.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.