Yunnancoelacanthus acrotuberculatus, Wen & Zhang & Hu & Benton & Zhou & Tao & Huang & Chen, 2013
|
publication ID |
https://doi.org/ 10.4202/app.2011.0066 |
|
persistent identifier |
https://treatment.plazi.org/id/03FC3C20-DF40-FFA4-FFB5-FA39FF5982DB |
|
treatment provided by |
Felipe |
|
scientific name |
Yunnancoelacanthus acrotuberculatus |
| status |
sp. nov. |
Yunnancoelacanthus acrotuberculatus sp. nov.
Fig. 7 View Fig .
Etymology: The species name is derived from the characteristic sharp tubercles on the dermal bones of skull.
Holotype: LPV−12748, a complete specimen with skull in dorsal view. Its standard length is 255 mm.
Type horizon: Member II, Guanling Formation, Middle Triassic ( Nicoraella kockeli Zone , late Pelsonian, middle–late Anisian).
Type locality: Daaozi Village, Luoxiong Town, Luoping County, Qujing City, Yunnan Province, China (Zhang and Zhou 2008; Zhang et al. 2008; Hu et al. 2011).
Diagnosis.—A middle−sized coelacanth ( Fig. 7 View Fig ). The posterior parietals and anterior parietals have the same length. Opercle is big with a curved posteroventral margin. Preorbital present. Coronoid is semicircular in shape. Most dermal bones on roof of skull and cheek sculptured with strong sharp tubercles. The first dorsal fin has about 8 fin rays. Scales have fewer ridges on the exposed region.
Description
Skull and dermal bones of snout.—The skull is preserved in dorsal view. The roof of the skull is composed of a pair of postparietals, posterior parietals, anterior parietals and two pairs of nasals. The posterior parietals and the anterior parietals have nearly the same size. A large supratemporal fits into wide embayments in the postparietal. The extrascapular cannot be observed.
The supraorbital series consists of five elements, as seen on both sides of the skull. The posterior two of them form the upper margin of orbit. Three tectals follow. They are excluded from the orbital margin, articulating with the lateral rostral. The triangular preorbital articulates ventrally with the first tectal.
Cheek.—The lachrymojugal forms the entire ventral border of the orbit. It extends forward to meet the posterior border of the lateral rostral. The posterior end meets the postorbital and squamosal at their junction. The postorbital is semicircular. Below the postorbital is the squamosal, which is roughly rectangular in shape and larger than the postorbital. The preopercle is not complete on the right side.
The opercle is subtriangular in shape with a curved posteroventral margin.
The most distinctive feature is that most of the dermal bones of the skull are decorated by not only strong oval tubercles, but also some sharp ones. This is different from any other coelacanth.
Mandible.—The dorsal part of angular is overlapped by the lachrymojugal. The semicircular coronoid does not lie in its original place, having been shifted post−mortem, and it overlaps the ventral side of the gular. The dentition resembles Chinlea (Schaeffer 1967) , and is different from Axelia, Maylacanthus , and Scleracanthus (Schaeffer 1952; Rieppel 1980). The margin of the precoronoid supports a cluster of robust, conically pointed teeth with striated caps. The teeth on the dorsomedial surface of the dentary and prearticular have the same shape as those on the margin of the precoronoid, but they are much smaller and finer. Several small rounded teeth on the parasphenoid are observed between the two anterior parietals.
Pectoral girdle.—In the pectoral girdle, only a strong cleithrum and extracleithrum can be observed. The ventral region is pressed under the opercle.
Fins.—The pectoral fin is lobe−shaped. There are 22 fin rays, most of which are segmented for over half of their length. Pelvic fins are positioned posteriorly to the first dorsal fin, which is different from Laugia and Piveteauia (Rieppel 1980, Geng et al. 2009). They are also lobate in shape, consisting of 20 fin rays. The first dorsal fin contains about 8 fin rays, resembling Whiteia . The plate of the first dorsal fin is not preserved. There are 18 lepidotrichial rays in the second dorsal fin. Its plate is forked. Only 5 rays can be counted in the anal fin. The caudal fin has 16 rays in the upper lobe, 14 rays in the lower lobe, and 26 rays in the supplementary lobe. Longitudinal tubercles decorate the lepidotrichial rays of the first dorsal fin, the upper lobe and lower lobe of the caudal fin. Axial skeleton.—There are 11 neural spines between the second dorsal fin and the upper lobe of the caudal fin. In addition, 14 haemal spines are distributed between the pelvic fin and the anal fin according to the traces left.
Scalation.—The ligulate scales have a varying number of elongated hollow ridges in the exposed region. The number of ridges is more like Diplurus than Luopingcoelacanthus (Schaeffer 1952) . In the area between the first dorsal fin and the basal plate of the second dorsal fin, and the posterior region of caudal fin, the scales only have one ridge. In the other areas, scales usually have three to seven ridges. As in other coelacanths, the scales are decorated by fine, parallel striae on the covered region.
http://dx.doi.org/10.4202/app.2011.0066
Discussion.—It is clear that LPV−12748 cannot be ascribed to Luopingcoelacanthus , because these taxa differ in dentary, lachrymojugal, number of rays of the first dorsal fin, and decoration on dermal bones and scales. The feature which most closely resembles Luopingcoelacanthus is the semicircular coronoid.
We have lost some information in the extrascapular, palate, and basal plates of the unpaired fins. However, we still find that the new specimen is similar to Guizhoucoelacanthus in some respects. They have similar supraorbital series, postorbital, squamosal, parietal shield, lower jaw, and number of rays of the first dorsal fin. Guizhoucoelacanthus has been assigned to the coelacanth family Whiteiidae by Geng et al. (2009). However, Guizhoucoelacanthus is a large coelacanth, with standard length about 500 mm, compared to 250 mm for our Yunnancoelacanthus . Because of the position of postorbital and pelvic fins, Yunnancoelanthus cannot be ascribed to either Whiteia or Piveteauia . As a result, a new genus is erected, based on the unique ornamentation on the skull.
Geographic and stratigraphic range.— Type locality and horizon only.
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.