Bibarba, Chen & Chen, 2007
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publication ID |
https://doi.org/ 10.1093/zoolinnean/zlaa073 |
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DOI |
https://doi.org/10.5281/zenodo.5307191 |
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persistent identifier |
https://treatment.plazi.org/id/9C56FE47-383C-FFCC-FEB4-F921FE10FE29 |
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treatment provided by |
Felipe |
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scientific name |
Bibarba |
| status |
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OSTEOLOGY OF BIBARBA View in CoL View at ENA
The cranial skeleton of Bibarba is typical of cobitids sensu Sawada (1982), with an evident metapterygoid– quadrate fenestra in the suspensorium and an interorbital fenestra in the neurocranium ( Figs 4 View Figure 4 , 5 View Figure 5 ).
In cave-dwelling B. parvoculus , the pterosphenoid forms the posterior rim of the interorbital fenestra, dorsoventrally separating the frontal and the parasphenoid, and posteriorly contacting only the sphenotic ( Fig. 4C View Figure 4 ). The bifurcate pharyngeal process of the basioccipital is short and tapers to an end at a vertical approximately anterior to centrum 2 + 3 ( Fig. 4C, F View Figure 4 ). The entopterygoid is a slim bone with a blade-like posterior part and, anteriorly, articulates with the palatine and, posteriorly, with the metapterygoid ( Fig. 4D View Figure 4 ). The posteroventral process of ceratobranchial 5 (pharyngeal bone) extends ventrally, forming a right angle with the ventral limb ( Fig. 4E View Figure 4 ). A single fontanelle enclosed by paired frontals, paired parietals and the supraoccipital is on the roof of the skull ( Fig. 6C View Figure 6 ). The anterior part of the frontal is narrow at the orbital region and about 36% as wide as the posterior part ( Fig. 6C, F View Figure 6 ). The suborbital spine is relatively stout. A weakly ossified supraorbital with a grey value similar to that of the sclera ring in the 3D rendering ( Fig. 6C View Figure 6 ) is at a vertical approximately anterior to the laterocaudal process of the suborbital spine. In the caudal skeleton, there are five hypurals, with hypurals 4 and 5 fused (in all specimens except for one female with hypurals 4 and 5 separate) ( Fig. 4H View Figure 4 ). The vertebral count (including the first four centra forming the Weberian apparatus and the last pleural centrum) is 45 (N = 2) or 46 (N = 2).
In surface-dwelling B. bibarba , the skeleton is similar but has the following differences. The bifurcate pharyngeal process of the basioccipital is short and stout, ending at a vertical approximately anterior to centrum 1 ( Fig. 5C, F View Figure 5 ). The posterior part of the entopterygoid is shallow ( Fig. 5D View Figure 5 ). The posteroventral process of the pharyngeal extends posteriorly, forming an obtuse angle with its ventral limb ( Fig. 5E View Figure 5 ). The anterior frontal is narrower, about 20% as wide as the posterior part ( Fig. 6I, L View Figure 6 ). The vertebral count is 39 (N = 2).
Sexual dimorphism is demonstrated in the pectoral fin and in the pectoral girdle, nasal bones and anterior intermuscular bones based on the two males and four females ( Figs 1C, D View Figure 1 , 5C, F View Figure 5 , 6 View Figure 6 ). In the pectoral fin, a duplication of the lamina circularis on the second and third pectoral rays occurs in males ( Fig. 1C, D View Figure 1 ). In the pectoral girdle, the coracoids, mesocoracoid and scapula are much stouter in the male ( Fig. 6D, E, J, K View Figure 6 ) and all are fused with the cleithrum in surfacedwelling B. bibarba ( Fig. 6J, K View Figure 6 ), but autogenous in cave-dwelling B. parvoculus ( Fig. 6D, E View Figure 6 ). The lateral lamina at the ventral limb of the cleithrum is smaller in males than in females of B. bibarba ( Fig. 6H, K View Figure 6 ). In addition, a vertically positioned lamina derived from the second pectoral radial contacting the mesocoracoid ( Fig. 6A, D, G, J View Figure 6 ), is much stronger in males ( Fig. 6D, J View Figure 6 ). In the neurocranium, a slim laterally convex nasal is lateral to the supraethmoid–ethmoid complex, which is stouter in males than in females of B. bibarba ( Fig. 6I, L View Figure 6 ), but similar in male and female B. parvoculus ( Fig. 6C, F View Figure 6 ). The anterior intermuscular bone associated with vertebrae 4 and 5 is ramified and hatchet-like and stouter in male than in female B. bibarba ( Fig. 5C, F View Figure 5 ), but similar in male and female B. parvoculus ( Fig. 4C, F View Figure 4 ).
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