Abstract
BackgroundThe classification of gobioid fishes is still under discussion. Several lineages, including the Eleotridae and Butidae, remain difficult to characterize because synapomorphies are rare (Eleotridae) or have not yet been determined (Butidae). Moreover, the fossil record of these groups is scarce.ResultsExceptionally well-preserved fish fossils with otoliths in situ from uppermost Oligocene sediments (≈23–24 Mio. y. ago) in Southern France provide the most in-depth description of a fossil gobioid to date. The species was initially described as Cottus aries Agassiz, then transferred to †Lepidocottus Sauvage, and subsequently assigned to Gobius. Based on a comparative analysis of meristic, osteological and otolith data, this species most likely is a member of the family Butidae. This discovery is important because it represents the first record of a fossil butid fish based on articulated skeletons from Europe.SignificanceThe Butidae and Eleotridae are currently distributed in W-Africa, Madagascar, Asia and Australia, but they do not appear in Europe and also not in the Mediterranean Sea. The new results indicate that several species of the Butidae thrived in Europe during the Oligocene and Early Miocene. Similar to the recent Butidae and Eleotridae, these fishes were adapted to a wide range of salinities and thrived in freshwater, brackish and marginal marine habitats. The fossil Butidae disappeared from Europe and the Mediterranean and Paratethys areas during the Early Miocene, due probably to their lack of competitiveness compared to other Gobioidei that radiated during this period of time. In addition, this study documents the great value of otoliths for gobioid systematics.
Highlights
The Gobioidei represents one of the most species-rich vertebrate suborders, with approximately 2,000 extant species thriving in marine, estuarine and freshwater habitats [1,2]
Preliminary Remark The studied specimens are determined as {Lepidocottus aries (Agassiz), because they largely correspond to the original description of this species by Agassiz [34] (p. 12, 186–187) and were found at the type locality (Aix-en-Provence)
Agassiz has indicated that his new species Cottus aries is figured on Plate 18; this plate was never printed and no figure of the holotype exists
Summary
The Gobioidei represents one of the most species-rich vertebrate suborders, with approximately 2,000 extant species (belonging to .270 genera) thriving in marine, estuarine and freshwater habitats [1,2]. Their classification was initially based on typical complements of morphological characters Thacker [13] used molecular data to elevate the two previous subfamilies of the Eleotridae (Butinae, Eleotrinae, see [1,7,20]) to the rank of family, Butidae and Eleotridae (see [21]), but synapomorphies based on morphological traits have not yet been determined for the Butidae.
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