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Papers by Ole Andreas Hoel

Norsk Geologisk Tidsskrift, 1999

Norsk Geologisk Tidsskrift, 1999

Paleontology Journal, 2014

Leptaenine brachiopods are common and widespread on Gotland. Lepidoleptaena poulseni and Leptaena... more 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.

Norsk Geologisk Tidsskrift

The occurrence in the Arenig of the Oslo Region of the typically east Baltic trilobite Megistaspi... more The occurrence in the Arenig of the Oslo Region of the typically east Baltic trilobite Megistaspis (Rhinoferus) hyorrhina (Leuchtenberg, 1843) is con­ firmed. The Norwegian specimens exhibit a range of variation just as wide as that seen in the east Baltic. The visual field is estimated and found to overlap posteriorly and 20° above horizontal. The glabellar tubercle in asaphids is considered to have functioned as a pressure-sensitive organ. The swelling of the posterior part of the glabella in some specimens, may have been to lift this organ as high as possible. This interpretation, together with the elevated eyes and the flattened exoskeleton, suggest a shallow infaunal life habit. lntroduction Megistaspis (Rhinoferus) hyorrhina (Leuchtenberg, 1843) has previously been considered a typical eastern Baltic species, common on the island of Oland, but rare in central Sweden and absent from the deeper-water envi­ ronment of the Oslo Region (Tjernvik & Johansson 1980, p. 189). Recently,...

Paläontologische Zeitschrift, 2011

Twelve species of Brachiopods are described from the Silurian of Gotland, six furcitellinines and... more Twelve species of Brachiopods are described from the Silurian of Gotland, six furcitellinines and six ''strophodontids.'' One is new-Strophodonta hoburgensis n. sp. The furcitellinines are moderately common and diverse in the lower part of the succession, but the last species disappears in the middle Hemse beds (*middle Ludlow). Three genera are represented: Bellimurina, Pentlandina and Katastrophomena, with the species and subspecies B. wisgoriensis, P. tartana, P. loveni, P. lewisii lewisii, K. penkillensis and K. antiquata scabrosa. Most of the taxa are confined to low energy environments, but P. loveni was evidently specialized for the high energy reef environments of the Högklint Formation. B. wisgoriensis displays environmentally induced morphological variability in developing strong, frilly growth lamellae in high-energy environments. The ''strophodontids,'' although belonging to three different families, share a common morphology consisting of denticles along the hinge line, a semi-circular outline, unequally to finely costellate ornament and, most importantly, a concavo-convex profile with both valves of the same curvature, enclosing a very small body chamber. Two leptostrophiids are generalists, occurring in both highand low-energy environments and with long stratigraphical ranges [Mesoleptostrophia filosa; latest Llandovery through the entire Ludlow. Brachyprion (Brachyprion) semiglobosa; latest Llandovery to latest Wenlock]. The third leptostrophiid (Brachyprion (Erinostrophia) walmstedti) is short ranged and occurs in low-energy environments in the latest Llandovery. The species belonging to the Strophodontidae (Strophodonta hoburgensis n. sp.) and Shaleriidae [Shaleria (Janiomya) ornatella and S. (Shaleriella) ezerensis] occur only in high-energy environments and have a short range within the late Ludlow.

Paläontologische Zeitschrift, 2005

Strophomenid brachiopods belonging to the genera Leptaena and Lepidoleptaena are described from t... more Strophomenid brachiopods belonging to the genera Leptaena and Lepidoleptaena are described from the uppermost Llandovery -Ludlow succession of Gotland, Sweden. In Gotland, Lepidoleptaena comprises the single species L. poulseni, and Leptaena includes four species: L. rhomboidalis, L. sperion, L. depressa and L. parvirugata n. sp. L. depressa shows a considerable amount of morphological variation, which is recognised in the two new subspecies Leptaena depressa visbyensis n. ssp. from the Llandoverian -Wenlockian Visby Formation, and L. depressa lata n. ssp. from the mid-Wenlockian Slite Group. The distribution of the different species is largely substrate-dependent, with Leptaena rhomboidalis and Lepidoleptaena poulseni adapted to high-energy environments with firm substrates, whereas the remaining species preferred fine-grained substrates in low-energy environments.

Geobios, 2007

Dorsal valves of the cementing strophomenide brachiopods Leptaenoidea silurica Hedström and Lilje... more Dorsal valves of the cementing strophomenide brachiopods Leptaenoidea silurica Hedström and Liljevallia gotlandica Hedström are described for the first time, and it is shown that both these species could also live ambitopically. The lower Wenlock Scamnomena rugata (Lindström) represents young individuals of the ambitopic variant of Leptaenoidea silurica, and is placed in synonymy, resulting in the valid name for the taxon being Leptaenoidea rugata. The range of this species now spans the whole Wenlock, from the upper Visby Formation to the Klinteberg Formation, and possibly even into the Ludlow. Ambitopic gerontic specimens of L. rugata develop very thick shells, in which the ventral valves have strong curvature, and become deeper not by geniculation but by successive mantle retractions and subsequent re-growth, in a way similar to that of atrypides. This shape was probably an adaptation to ''floating'' on softer substrates. The thickened gerontic dorsal valves have well-developed lophophoral support, showing the shape of the lophophore, which comprises two branches that curve inwards and then backwards; the lophophore was probably ptycholophous and similar to that in living members of the Thecideidina. Ambitopic specimens of Liljevallia could grow to a much larger size than cementing forms, where the dorsal valves have very large, posterior-facing cardinal process lobes and deeply impressed muscle fields and anterior scars. The presence of a ventral process and long, posteroventrally elongated cardinal process lobes, and the absence of dental plates reveals that Liljevallia was probably an early member of the Douvillinidae and is thus removed from the Leptaenoideidae. # 2007 Elsevier Masson SAS. All rights reserved.

Norsk Geologisk Tidsskrift, 1999

Norsk Geologisk Tidsskrift, 1999

Paleontology Journal, 2014

Leptaenine brachiopods are common and widespread on Gotland. Lepidoleptaena poulseni and Leptaena... more 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.

Norsk Geologisk Tidsskrift

The occurrence in the Arenig of the Oslo Region of the typically east Baltic trilobite Megistaspi... more The occurrence in the Arenig of the Oslo Region of the typically east Baltic trilobite Megistaspis (Rhinoferus) hyorrhina (Leuchtenberg, 1843) is con­ firmed. The Norwegian specimens exhibit a range of variation just as wide as that seen in the east Baltic. The visual field is estimated and found to overlap posteriorly and 20° above horizontal. The glabellar tubercle in asaphids is considered to have functioned as a pressure-sensitive organ. The swelling of the posterior part of the glabella in some specimens, may have been to lift this organ as high as possible. This interpretation, together with the elevated eyes and the flattened exoskeleton, suggest a shallow infaunal life habit. lntroduction Megistaspis (Rhinoferus) hyorrhina (Leuchtenberg, 1843) has previously been considered a typical eastern Baltic species, common on the island of Oland, but rare in central Sweden and absent from the deeper-water envi­ ronment of the Oslo Region (Tjernvik & Johansson 1980, p. 189). Recently,...

Paläontologische Zeitschrift, 2011

Twelve species of Brachiopods are described from the Silurian of Gotland, six furcitellinines and... more Twelve species of Brachiopods are described from the Silurian of Gotland, six furcitellinines and six ''strophodontids.'' One is new-Strophodonta hoburgensis n. sp. The furcitellinines are moderately common and diverse in the lower part of the succession, but the last species disappears in the middle Hemse beds (*middle Ludlow). Three genera are represented: Bellimurina, Pentlandina and Katastrophomena, with the species and subspecies B. wisgoriensis, P. tartana, P. loveni, P. lewisii lewisii, K. penkillensis and K. antiquata scabrosa. Most of the taxa are confined to low energy environments, but P. loveni was evidently specialized for the high energy reef environments of the Högklint Formation. B. wisgoriensis displays environmentally induced morphological variability in developing strong, frilly growth lamellae in high-energy environments. The ''strophodontids,'' although belonging to three different families, share a common morphology consisting of denticles along the hinge line, a semi-circular outline, unequally to finely costellate ornament and, most importantly, a concavo-convex profile with both valves of the same curvature, enclosing a very small body chamber. Two leptostrophiids are generalists, occurring in both highand low-energy environments and with long stratigraphical ranges [Mesoleptostrophia filosa; latest Llandovery through the entire Ludlow. Brachyprion (Brachyprion) semiglobosa; latest Llandovery to latest Wenlock]. The third leptostrophiid (Brachyprion (Erinostrophia) walmstedti) is short ranged and occurs in low-energy environments in the latest Llandovery. The species belonging to the Strophodontidae (Strophodonta hoburgensis n. sp.) and Shaleriidae [Shaleria (Janiomya) ornatella and S. (Shaleriella) ezerensis] occur only in high-energy environments and have a short range within the late Ludlow.

Paläontologische Zeitschrift, 2005

Strophomenid brachiopods belonging to the genera Leptaena and Lepidoleptaena are described from t... more Strophomenid brachiopods belonging to the genera Leptaena and Lepidoleptaena are described from the uppermost Llandovery -Ludlow succession of Gotland, Sweden. In Gotland, Lepidoleptaena comprises the single species L. poulseni, and Leptaena includes four species: L. rhomboidalis, L. sperion, L. depressa and L. parvirugata n. sp. L. depressa shows a considerable amount of morphological variation, which is recognised in the two new subspecies Leptaena depressa visbyensis n. ssp. from the Llandoverian -Wenlockian Visby Formation, and L. depressa lata n. ssp. from the mid-Wenlockian Slite Group. The distribution of the different species is largely substrate-dependent, with Leptaena rhomboidalis and Lepidoleptaena poulseni adapted to high-energy environments with firm substrates, whereas the remaining species preferred fine-grained substrates in low-energy environments.

Geobios, 2007

Dorsal valves of the cementing strophomenide brachiopods Leptaenoidea silurica Hedström and Lilje... more Dorsal valves of the cementing strophomenide brachiopods Leptaenoidea silurica Hedström and Liljevallia gotlandica Hedström are described for the first time, and it is shown that both these species could also live ambitopically. The lower Wenlock Scamnomena rugata (Lindström) represents young individuals of the ambitopic variant of Leptaenoidea silurica, and is placed in synonymy, resulting in the valid name for the taxon being Leptaenoidea rugata. The range of this species now spans the whole Wenlock, from the upper Visby Formation to the Klinteberg Formation, and possibly even into the Ludlow. Ambitopic gerontic specimens of L. rugata develop very thick shells, in which the ventral valves have strong curvature, and become deeper not by geniculation but by successive mantle retractions and subsequent re-growth, in a way similar to that of atrypides. This shape was probably an adaptation to ''floating'' on softer substrates. The thickened gerontic dorsal valves have well-developed lophophoral support, showing the shape of the lophophore, which comprises two branches that curve inwards and then backwards; the lophophore was probably ptycholophous and similar to that in living members of the Thecideidina. Ambitopic specimens of Liljevallia could grow to a much larger size than cementing forms, where the dorsal valves have very large, posterior-facing cardinal process lobes and deeply impressed muscle fields and anterior scars. The presence of a ventral process and long, posteroventrally elongated cardinal process lobes, and the absence of dental plates reveals that Liljevallia was probably an early member of the Douvillinidae and is thus removed from the Leptaenoideidae. # 2007 Elsevier Masson SAS. All rights reserved.