50 



R. HUYS AND W. LEE 



sexual dimorphism Onychocamptus Daday and the Laophonte comuta-group invariably form a clade in opposition to all other 

 Laophontinae, implying polyphyly of the type genus. 



The Esolinae is a relict group, cosmopolitan in distribution and displaying a complex ecological radiation. Analysis at species 

 level identified Archilaophonte Willen as the basal node and Mourephonte Jakobi as the terminal branch, and provided strong 

 support for the paraphyly of Esola Edwards. Relationships within the Esolinae are largely determined by patterns of transformed 

 integumental pores, sexual dimorphism of P2-P3 and caudal rami, segmentation of 2 antennule and PI exopod, and 9 P5 

 armature. 



The genus Esola is redefined to include a crown-group of 8 species, the distribution of which primarily coincides with the 

 circumglobal Tethyan belt. The universally accepted cosmopolitan distribution of the type species E. longicauda Edwards is 

 rejected on morphological grounds, resulting in the resurrection of E. bulbifera (Norman), the upgrading of E. longicauda 

 galapagoensis Mielke and the recognition of four species previously confounded with the type (E. vervoorti sp. nov., E. lobata 

 sp. nov., E. canalis sp. nov.) or based on new collections (E. profunda sp. nov.). Laophonte rhodiaca Brian is regarded as a likely 

 synonym of E. bulligera. 



Both E. hirsuta (Thompson & A. Scott) and E. bulligera (Farran) are allocated to monotypic genera, Applanola gen. nov. and 

 Corbulaseta gen. nov., respectively. The mediterranean E. rosei (Monard) is considered a junior subjective synonym of the 

 northwestern European C. bulligera. E. spelaea (Chappuis), representing an isolated freshwater incursion in Apulian caves, is 

 transferred to Troglophonte gen. nov. and various ambiguities contained in its original description are reviewed. Bathyesola 

 compacta gen. et sp. nov. was discovered at 2765 m depth on the North Fiji Ridge, representing the deepest record for the family 

 thus far. E. typhlops (Sars) forms an exclusively Atlantic boreo-arctic clade with E. longiremis (T. Scott) and Esola sp. sensu 

 Chislenko (1967). A fourth species, A. hamondi from Norfolk, is added to this group which is accorded generic rank (Archesola 

 gen. nov.) on the basis of neotenic development of the male P3 endopod. 



A generic key to the Esolinae and a review of their ecological radiation are presented. 



INTRODUCTION 



Laophontids comprise one of the six extant families of the 

 Laophontoidea (Huys & Lee, 1999). They represent by far the most 

 speciose group in this superfamily, currently accommodating 269 

 valid species and subspecies in 57 genera (Lee & Huys, 1999). 

 Laophontidae are essentially marine, free-living, benthic and restricted 

 to phytal or shallow subtidal and intertidal habitats. Their success in 

 the deep sea is modest and only very few lineages have radiated into 

 freshwater or have entered into associations with invertebrate hosts. 

 The current rate of new species descriptions indicates that only a 

 moderate fraction of their true diversity is known. 



Lang's (1948) phylogenetic scheme of the Laophontidae included 

 only 19 genera, six of which being placed in other, existing or new, 

 families since (Hicks, 1988a; Huys, 1990a,6; Huys & Lee, 1999; 

 Huys & Willems, 1989). Although this re-allocation has signifi- 

 cantly refined the taxonomic concept of the family and hence its 

 monophyletic status is no longer a matter of dispute (Huys & Lee, 

 1999), the relationships between genera are usually not well under- 

 stood. The justification for creating new genera has traditionally 

 been based on a purely comparative approach, usually by consider- 

 ing a particular combination of characters as unique, rather than on 

 phylogenetic grounds. Some authors (e.g. Noodt, 1958) attempted 

 to unravel the relationships within particular lineages but their kind 

 of analysis was not cladistic and considered only a limited number of 

 characters. Others considered a thorough revision of the type genus 

 Laophonte Philippi as a conditio sine qua non for a phylogenetic 

 analysis incorporating all genera (Hicks, 19886; Willen, 1996). 



The recent discovery of the primitive genus Archilaophonte in the 

 Antarctic Weddell Sea (Willen, 1995) has shed some light on the 

 early evolution of the family. Willen (1995) proposed an evolution- 

 ary scenario placing Archilaophonte and Esola as sistertaxa at the 

 base of the laophontid tree. Her analysis did not include the genus 

 Mourephonte Jakobi, left the potential paraphyly of Esola unchal- 

 lenged and was based on few characters. In this paper we have first 

 concentrated on the relationships within the genus Esola and its 

 affinity to Mourephonte and Archilaophonte. In order to resolve the 

 basal dichotomy in laophontid evolution we found it necessary to 

 run the analysis at the species level. Re-examination of the majority 

 of these species revealed important new taxonomic information 



which reinforces the early split of two major lineages in the 

 Laophontidae. In this paper we propose a new hypothesis of basal 

 evolutionary relationships in the Laophontidae which will hopefully 

 provide a solid baseline for future studies addressing the phylogeny 

 of the more advanced crown-group taxa. 



MATERIAL AND METHODS 



Specimens were dissected in lactic acid and the dissected parts were 

 mounted on slides in lactophenol mounting medium. Preparations 

 were sealed with Glyceel or transparent nail varnish. All drawings 

 have been prepared using a camera lucida on a Zeiss Axioskop, 

 Leitz Dialux or Leitz DMR microscope equipped with differential 

 interference contrast. 



Esola bulbifera, Applanola hirsuta and Archesola typhlops were 

 examined with a Hitachi S-800 or Philips XL30 scanning electron 

 microscope. Specimens were prepared by dehydration through 

 graded acetone, critical point dried, mounted on stubs and sputter- 

 coated with gold or palladium. 



The descriptive terminology is adopted from Huys et al. (1996). 

 Abbreviations used in the text are: Al, antennule; A2, antenna; ae, 

 aesthetasc; exp, exopod; enp, endopod; P1-P6, first to sixth 

 thoracopod; exp(enp)-l(2, 3) to denote the proximal (middle, distal) 

 segment of a ramus. Type series are deposited in the collections of 

 The Natural History Museum, London (BMNH), the Museum 

 National d'Histoire Naturelle, Paris (MNHNP) and the National 

 Museum of Natural History, Smithsonian Institution, Washington, 

 D.C. (NMNH). Scale bars in figures are indicated in pm. 



GENERIC DIAGNOSES AND SPECIES 

 DESCRIPTIONS 



Family LAOPHONTIDAE T. Scott, 1905 



Genus Esola Edwards, 1891 



Edwards (1891) described Esola longicauda from an unknown, 

 shallow coastal locality in the Bahamas. Although the author found 

 the species embedded in mucus inside the body cavity of the 





