Editorial Type:
Article Category: Research Article
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Online Publication Date: 27 Sept 2013

The Genus Typhlobelus: Monophyly and Taxonomy, with Description of a New Species with a Unique Pseudotympanic Structure (Teleostei: Trichomycteridae)

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Page Range: 441 – 453
DOI: 10.1643/CI-13-007
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The psammophilic trichomycterid genus Typhlobelus is rediagnosed on the basis of additional synapomorphic characters, including: 1) the premaxilla displaced posteriorly, and connected to shaft of the mesethmoid rather than to its anterior tip; 2) the premaxilla with complex tridimensional shape, with a large dorsal process directed mesially and bearing teeth (when present) on the lateral end only; 3) the dentary portion of the coronoid process expanded into a broad plate; 4) the palatine club-shaped and oriented obliquely relative to the longitudinal axis of the skull; 5) the semi-discoidal anterior portion of the mesethmoid; 6) the laminar anterior ascending process of the quadrate lacking a cartilaginous tip; 7) hyomandibula with a long posterior process; 8) the neural arch of the Weberian complex ring-like and forming two large dorsal foramina at its border with the supraoccipital; and 9) the basibranchials and hypobranchials poorly differentiated or absent. Additional diagnostic characters are presented for the species currently included in Typhlobelus. A new species of the genus, Typhlobelus auriculatus, from the Rio Xingu in northern Brazil, is uniquely diagnosed from all other trichomycterids, and probably from all other catfishes, by the presence of a well-defined lateral pit immediately posterior to the head, representing a modified pseudotympanus connected by a superficial groove to a pit entering the skull. The species is also unique in the lack of any laterosensory pores on the body or head. The new species is further distinguished from its congeners by the absence of an anal fin and by the presence of opercular odontodes, in addition to other characters of internal and external anatomy.

Copyright: 2013 by the American Society of Ichthyologists and Herpetologists
Fig. 1.
Fig. 1.

Upper jaws and anterior portion of skull in Typhlobelus auriculatus, ventral view, paratype, MZUSP 109847. Abbreviations: let, lateral ethmoid; lig, ligament; max, maxilla; mes, mesethmoid; orb, orbitosphenoid; pal, palatine; par, parasphenoid; pmx, premaxilla. Scale bar  =  0.5 mm.

Fig. 2.
Fig. 2.

Lower jaws, mesial views. (A) Typhlobelus auriculatus, paratype, MZUSP 109847; (B) T. ternetzi, paratype, CAS 11119. Abbreviations: ang, angular; den, dentary. Scale bar  =  0.5 mm.

Fig. 3.
Fig. 3.

Anterior portion of mesethmoid in species of Typhlobelus, dorsal views. (A) Typhlobelus auriculatus, paratype, MZUSP 109847; (B) T. guacamaya, paratype, MZUSP 81770; (C) T. lundbergi, paratype, MZUSP 84305; (D) T. macromycterus, holotype, MNRJ 12129; (E) T. ternetzi, paratype, CAS 11119. Scale bar  =  0.5 mm.

Fig. 4.
Fig. 4.

Suspensoria in species of Typhlobelus, ventrolateral views. (A) Typhlobelus auriculatus, paratype, MZUSP 109847; (B) T. guacamaya, paratype, MZUSP 81770; (C) T. ternetzi, paratype, CAS 11119. Abbreviations: hyo, hyomandibula; int, interopercle; op, opercle; pre, preopercle; qua, quadrate. Scale bar  =  0.5 mm.

Fig. 5.
Fig. 5.

Lower branchial arches of Typhlobelus auriculatus, dorsal view. Dense stippling represents cartilage, paratype, MZUSP 109847. Abbreviations: bb4, basibranchial 4; cb1–5, ceratobranchial 1 to 5; cop, branchial copula. Scale bar  =  0.5 mm.

Fig. 6.
Fig. 6.

Typhlobelus auriculatus, new species, holotype, INPA 12929, lateral view. Scale bar  =  1 mm.

Fig. 7.
Fig. 7.

Typhlobelus auriculatus, new species, paratype, MZUSP 109847, SEM preparation, dorsal view of head. Snout preserved in dorsally bent position (also applies to Figs. 8, 10). Scale bar  =  100 μ.

Fig. 8.
Fig. 8.

Typhlobelus auriculatus, new species, paratype, MZUSP 109847, SEM preparation, ventral view of head. Scale bar  =  100 μ.

Fig. 9.
Fig. 9.

Typhlobelus auriculatus, new species, paratype, MZUSP 109847, SEM preparation, close up dorsal view of nares and base of nasal barbel. Right nares, anterior to left. Scale bar  =  100 μ.

Fig. 10.
Fig. 10.

Typhlobelus auriculatus, new species, paratype, MZUSP 109847, SEM preparation, lateral view of head, left side. Scale bar  =  100 μ.

Fig. 11.
Fig. 11.

Typhlobelus auriculatus, new species, paratype, MZUSP 109847, SEM preparation, close up of dorsolateral view of tympanic recess, anterior to left. Scale bar  =  100 μ.

Fig. 12.
Fig. 12.

Typhlobelus auriculatus, new species, paratype, MZUSP 109847, SEM preparation, close up ventral view of anus (left) and urogenital papilla (right), anterior to left. Scale bar  =  100 μ.

Fig. 13.
Fig. 13.

Geographical distribution and type locality of Typhlobelus auriculatus, Rio Xingu at Arroz Cru.

Fig. 14.
Fig. 14.

Habitat and type locality of Typhlobelus auriculatus, Rio Xingu at Arroz Cru. Specimens were found buried in sand in area at bottom left of photograph. Photo by J. Zuanon, 8 October 1996.

Fig. 15.
Fig. 15.

Opercle and interopercle of: (A) T. lundbergi, paratype, MZUSP 84305; (B) T. macromycterus, holotype, MNRJ 12129. Abbreviations: int, interopercle; op, opercle. Scale bar  =  0.5 mm.

Contributor Notes

Associate Editor: R. E. Reis.

Received: 24 Jan 2013
Accepted: 29 Mar 2013
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