%0 Journal Article
%T Palaeobiology of Silurian Leptaeninae (Brachiopoda) from Gotland, Sweden
%A Ole A. Hoel
%J Paleontology Journal
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/716053
%X Leptaenine brachiopods are common and widespread on Gotland. Lepidoleptaena poulseni and Leptaena rhomboidalis retained a functional apical pedicle throughout ontogeny, and both had strong adductor muscles and robust ornamentation, allowing them to occupy shallow water and high energy environments. A pedicle-shortening muscle is present within the pedicle tube of Leptaena rhomboidalis. Leptaena sperion, L. depressa visbyensis, and L. depressa lata inhabited low energy environments, retaining very slender pedicles. L. depressa depressa and L. parvorugata atrophied the pedicle early and then lived ambitopically in deeper water. The presence or absence of the apical pedicle strongly influenced the cardinal process morphology. Leptaenine shells had a small gape. The lophophore was simple, similar to productids and Leptaenoidea. In closed valves, the inner epithelium of leptaenine trails remained exposed to the sea. This was probably important in gas exchange. The life position of pedically attached species was with the disc vertical. Some ambitopic specimens may have retained a similar attitude. Shells of L. depressa depressa and Lepidoleptaena poulseni commonly are encrusted by epibionts, apparently without problems for larger shells. Small shells are shown to have been killed by bryozoan epizoans. Repaired shell damage is rare on the disc but is common along the commisure. 1. Introduction The genus Leptaena is one of the most widespread and taxonomically diverse strophomenide brachiopods, with more than 50 named species worldwide and many more occurrences placed in open nomenclature. The temporal distribution is also notable in that the genus extends from the Middle Ordovician (Llanvirn) (e.g., [1]) into the Lower Devonian (Emsian) (e.g., [2, 3]), which amounts to a longevity of about 75 million years. In the Silurian succession of Gotland, Leptaena is a very common component of most brachiopod faunas from the late Llandovery to the Middle Ludlow, after which its role is taken over by the closely related Lepidoleptaena. The taxonomy of these two genera on Gotland has been revised elsewhere [4], following which the recognised species present in the Silurian of Gotland are Leptaena rhomboidalis, Wahlenberg [5]; L. depressa depressa Sowerby, [6]; L. depressa lata, Hoel [4]; L. depressa visbyensis, Hoel [4]; L. sperion, Bassett [7]; L. parvorugata, Hoel [4]; Lepidoleptaena poulseni, Kelly [8]; Lepidoleptaena sp. A and sp. B. In the course of that study several aspects of functional morphology and ecology came to light, which prompted the present paper.
%U http://www.hindawi.com/journals/paleontology/2014/716053/