Lophiiform fishes represent a highly diverse assemblage of taxa, most of which characterized by an extremely derived morphology and bizarre appearance. These fishes share a peculiar mode of feeding primarily exemplified by the configuration of the anteriormost part of the spinous dorsal fin that is cephalic in position and modified to serve as a luring apparatus. The whole order consists of 18 families distributed among five suborders: the Antennarioidei, Ceratioidei, Chaunacoidei, Lophioidei, and Ogcocephaloidei. The suborder Antannrioidei includes four families containing more than 50 living species, nearly all laterally-compressed, shallow-water, benthic forms. Within this suborder, members of the family Brachionichthyidae, also known as handfishes, constitute a distinct lineage, characterized by a relatively elongate and slightly compressed body, a prominent sail-like spinous dorsal fin and arm-like pectoral fin; the pectoral fins, together with the pelvic fins are used to walk along the substrate in a more or less typical tetrapod-like fashion. Today, handfishes are sedentary bottom-dwellers that inhabit the continental shelf of subtropical and warm temperate parts of Tasmania and southern and eastern Australia. Despite their narrow present-day distribution, low α-diversity and the general extreme rarity of lophiiform in the fossil record, brachionichthyids are well represented in the Eocene (Ypresian) micritic limestone of Monte Bolca. The first description of an Eocene handfish from Monte Bolca was provided by Baron Achille De Zigno in 1887 based on a single specimen from the Pesciara cave site. Subsequently, additional specimens have been cursorily described in a sparse series of publications during the XXth century. However, the unambiguous assignment of this material to family Brachionichthyidae was not demonstrated until 1981 (Pietsch 1981). A comprehensive revision of the known fossil handfish material in the collections of the Museo Civico di Storia Naturale, Verona, Museo di Geologia e Paleontologia, Università di Padova, Natural History Museum, London, Museum of Comparative Zoology, Harvard University, and Carnegie Museum, Pittsburgh showed the presence of two taxa; the large part of the material belongs to the species Histionotophorus bassani, while a couple of specimens in part and counterpart represent the type material of a new genus and species. The osteological study of Histionotophorus bassani revealed many new features as well as reinterpretations of some previously described skeletal parts. A phylogenetic analysis of brachionichthyid genera and representatives of the antennarioid families Antennariidae, Lophichthyidae and Tetrabrachiidae, using 36 morphological characters, strongly supported monophyly of brachionichthyids and antennarioids; the Brachionichthyidae represents the sister group of the other antennarioid families. Within the Brachionichthyidae, the two extant genera Brachionichthys and Sympterichthys form a species pair as do Histionotophorus and the new genus. Biogeographical considerations suggest that the present geographical range of handfishes can be considered a residual distribution of a temporally and spatially dynamic range shift.
Fossil handfish (Teleostei, Lophiiformes, Brachionichthyidae) from the Eocene of Monte Bolca, Italy
CARNEVALE, Giorgio;
2009-01-01
Abstract
Lophiiform fishes represent a highly diverse assemblage of taxa, most of which characterized by an extremely derived morphology and bizarre appearance. These fishes share a peculiar mode of feeding primarily exemplified by the configuration of the anteriormost part of the spinous dorsal fin that is cephalic in position and modified to serve as a luring apparatus. The whole order consists of 18 families distributed among five suborders: the Antennarioidei, Ceratioidei, Chaunacoidei, Lophioidei, and Ogcocephaloidei. The suborder Antannrioidei includes four families containing more than 50 living species, nearly all laterally-compressed, shallow-water, benthic forms. Within this suborder, members of the family Brachionichthyidae, also known as handfishes, constitute a distinct lineage, characterized by a relatively elongate and slightly compressed body, a prominent sail-like spinous dorsal fin and arm-like pectoral fin; the pectoral fins, together with the pelvic fins are used to walk along the substrate in a more or less typical tetrapod-like fashion. Today, handfishes are sedentary bottom-dwellers that inhabit the continental shelf of subtropical and warm temperate parts of Tasmania and southern and eastern Australia. Despite their narrow present-day distribution, low α-diversity and the general extreme rarity of lophiiform in the fossil record, brachionichthyids are well represented in the Eocene (Ypresian) micritic limestone of Monte Bolca. The first description of an Eocene handfish from Monte Bolca was provided by Baron Achille De Zigno in 1887 based on a single specimen from the Pesciara cave site. Subsequently, additional specimens have been cursorily described in a sparse series of publications during the XXth century. However, the unambiguous assignment of this material to family Brachionichthyidae was not demonstrated until 1981 (Pietsch 1981). A comprehensive revision of the known fossil handfish material in the collections of the Museo Civico di Storia Naturale, Verona, Museo di Geologia e Paleontologia, Università di Padova, Natural History Museum, London, Museum of Comparative Zoology, Harvard University, and Carnegie Museum, Pittsburgh showed the presence of two taxa; the large part of the material belongs to the species Histionotophorus bassani, while a couple of specimens in part and counterpart represent the type material of a new genus and species. The osteological study of Histionotophorus bassani revealed many new features as well as reinterpretations of some previously described skeletal parts. A phylogenetic analysis of brachionichthyid genera and representatives of the antennarioid families Antennariidae, Lophichthyidae and Tetrabrachiidae, using 36 morphological characters, strongly supported monophyly of brachionichthyids and antennarioids; the Brachionichthyidae represents the sister group of the other antennarioid families. Within the Brachionichthyidae, the two extant genera Brachionichthys and Sympterichthys form a species pair as do Histionotophorus and the new genus. Biogeographical considerations suggest that the present geographical range of handfishes can be considered a residual distribution of a temporally and spatially dynamic range shift.
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