Aurélie Pinton

Spine anatomy reveals the diversity of catfish through time: a case study of Synodontis (Siluriformes)

Synodontis (Mochokidae, Siluriformes) is a freshwater catfish endemic to Africa. The 118 extant species are present in almost all hydrographic basins. Some species are restricted to a single stream, whereas others have a vast distribution. Synodontis is known in the fossil record since the Miocene, and its history depends on the connections among African basins through time. The identification of species in the fossil record is essential to reconstruct this historical pattern. Catfish pectoral and dorsal spines are robust, they preserve well and they form most of the fossil remains for the genus Synodontis. Unfortunately, the criteria for the identification of extant Synodontis species are not applicable to fossil specimens. Here, we define 11 original morphological characters that permit to discriminate four extant species from the Chad-Chari hydrographic system. Six of these characters are defined on pectoral spines and five on dorsal spines. We then show that these characters can be used successfully for identifying fossil specimens. In particular, we present a case study in which we identify Synodontis cf. schall and Brachysynodontis cf. batensoda in the hominid-bearing sector Toros-Menalla (Late Miocene, northern Chad). We show that spine anatomy can be a powerful tool to recognise catfish species through time and thus to identify historical diversity pattern.

A Fish Assemblage from the Middle Eocene from Libya (Dur At-Talah) and the Earliest Record of Modern African Fish Genera.

In the early nineteen sixties, Arambourg and Magnier found some freshwater fish (i.e., Polypterus sp., Siluriformes indet. and Lates sp.) mixed with marine members in an Eocene vertebrate assemblage at Gebel Coquin, in the southern Libyan Desert. This locality, aged ca 37–39Ma and now known under the name of Dur At-Talah, has been recently excavated. A new fish assemblage, mostly composed of teeth, was collected by the Mission Paléontologique Franco-Libyenne. In this paper, we describe freshwater fish members including a dipnoan (Protopterus sp.), and several actinopterygians: bichir (Polypterus sp.), aba fish (Gymnarchus sp.), several catfishes (Chrysichthys sp. and a mochokid indet.), several characiforms (including the tiger fish Hydrocynus sp., and one or two alestin-like fish), and perciforms (including the snake-head fish Parachanna sp. and at least one cichlid). Together with the fossiliferous outcrops at Birket Qarun in Egypt, the Libyan site at Dur At-Talah reduces a 10-Ma chronological gap in the fossil record of African freshwater fish. Their fish assemblages overlap in their composition and thus constitute a rather homogenous, original and significant amount of new elements regarding the Paleogene African ichthyofauna. This supports the establishment of the modern African freshwater fish fauna during this time period because these sites mostly contain the earliest members known in modern genera.

Giants in a Minute Catfish Genus: First Description of Fossil Mochokus (Siluriformes, Mochokidae) in the Late Miocene of Chad, Including M. Gigas, sp. nov.

ABSTRACT The first Mochokus (Siluriformes, Mochokidae) remains of the fossil record are described, including a new species based on a sub-complete neurocranium discovered in the Late Miocene deposits of Toros-Menalla, Chad, Central Africa, dated to 7.0 Ma. Mochokus gigas, sp. nov., is the first fossil species described for the family Mochokidae, which is the largest family of African catfishes. The description is based on the comparison with the two living species of the genus, M. niloticus and M. brevis. Mochokus gigas, sp. nov., is a very large species presenting original features, notably on the pectoral spines and on the anterior part of the neurocranium. One of the apomorphies characterizing the modern genus Mochokus is found on the fossil: the root of the mesocoracoid arch is located on the posterior side of the vertical lamina of the coracoid and lacks any dorsally directed prominence. Several other Mochokus fossil remains, including nuchal plates, cleithra, and dorsal spines, are described and attributed to Mochokus, sp. indet., or Mochokus sp. Finally, and on the basis of preliminary observations of the fossil fish assemblages from different sites of Toros-Menalla, the lack of Mochokus fossil remains is discussed.

The bony anatomy of Chadian Synodontis (Osteichthyes, Teleostei, Siluriformes, Mochokidae): interspecific variations and specific characters

Pinton A. & Otero O. 2010. — The bony anatomy of Chadian Synodontis (Osteichthyes, Teleostei, Siluriformes, Mochokidae): interspecific variations and specific characters. Zoosystema 32 (2): 173-231. ABSTRACT The genus Synodontis Cuvier, 1816 (Siluriformes, Mochokidae) numbers about 120 species and is exclusive to the freshwater of Africa except Maghreb and Cape Province. It is one of the most widespread catfish of African freshwater. The Synodontis fossil record covers the last 18 Myr and most of the Synodontis fossil bones are found in a disarticulated state. The identification of the fossils at a specific level is so far impossible, because we lack an osteological study of the species. Here, we present the study of the osteology of eleven Synodontis species living in Chad: S. batensoda Rüppell, 1832, S. clarias (Linnaeus, 1758), S. courteti Pellegrin, 1906, S. eupterus Boulenger, 1901, S. filamentosus Boulenger, 1901, S. membranaceas (Geoffroy Saint-Hilaire, 1809), S. nigrita Valenciennes, 1840, S. ocellifer Boulenger, 1900, S. schall (Bloch & Schneider, 1801), S. sorex Günther, 1864 and S. violaceus Pellegrin, 1919. Each species is characterized based on its bony anatomy. The morphological variability within and between the species is discussed. The entire skeleton is described, bone by bone. A total of 61 osteological characters, both qualitative and quantitative are established. We emphasize the bones that are well preserved in the fossil, i.e. the mesethmoid, the lateral ethmoid, the frontal, the supraoccipital, the cleithrum, the pectoral spine, the middle nucal plate and the dorsal spine. As a first result, the Chadian Synodontis species can be recognized on the basis of bony characters only. Second, we are also able to attribute isolated bones to nominative species or to a group of species. At last, we note that no osteological character legitimates the distinction of the genera Hemisynodontis Bleeker, 1862 and Brachysynodontis Bleeker, 1862.

Evaluation of the fossil fish-specific diversity in a chadian continental assemblage: Exploration of morphological continuous variation in Synodontis (Ostariophysi, Siluriformes)

In the fossil record, the quantification of continuous morphological variation has become a central issue when dealing with species identification and speciation. In this context, fossil taxa with living representatives hold great promise, because of the potential to characterise patterns of intraspecific morphological variation in extant species prior to any interpretation in the fossil record. The vast majority of catfish families fulfil this prerequisite, as most of them are represented by extant genera. However, although they constitute a major fish group in terms of distribution, and ecological and taxonomic diversity, the quantitative study of their past morphological variation has been neglected, as fossil specimens are generally identified based on the scarcest remains, that is, complete neurocrania that bear discrete characters. Consequently, a part of freshwater catfish history is unprospected and unknown. In this study, we explored the morphological continuous variation of the humeral plate shape in Synodontis catfishes using Elliptic Fourier Analysis (EFA), and compared extant members and fossil counterparts. We analysed 153 extant specimens of 11 Synodontis species present in the Chad basin, in addition to 23 fossil specimens from the Chadian fossiliferous area of Toros Menalla which is dated around 7 Ma. This highly speciose genus, which is one of the most diversified in Africa, exhibits a rich fossil record with several hundred remains mostly identified as Synodontis sp. The analysis of the outline of the humeral plate reveals that some living morphological types were already represented in the Chad Basin 7 My ago, and allows for the discovery of extinct species. Beside illuminating the complex Neogene evolutionary history of Synodontis, these results underline the interest in the ability of isolated remains to reconstruct a past dynamic history and to validate the relevance of EFA as a tool to explore specific diversity through time. J. Morphol. 277:1486–1496, 2016.