The most widely distributed trilobite species: OrdovicianCarolinites genacinaca

Abstract

The distributions of trilobite species were controlled by a combination of habitat preferences and paleogeographic constraints, which tend to limit their extent. The Lower Ordovician trilobite Carolinites genacinaca Ross, 1951, however, had a remarkable range unequaled among polymerid trilobites; it has been recognized on all Ordovician paleocontinents. Its distribution has been explained by an epipelagic mode of life, based on evidence from functional morphology, analogy with modern pelagic crustaceans, and geological occurrence. In such a case, morphological identity throughout its range might be anticipated, if all occurrences can be postulated to be members of a single pandemic population. Rotational superimposition has been used to compare variation within samples drawn from Alberta, Spitsbergen, and Australia with a benchmark population from the western United States. All are morphometrically similar. By any criterion, specimens identical to the benchmark population are found within the Alberta, Spitsbergen and Australia samples, which represent the extremes of the species' geographic range. A lone cranidium from France, previously referred to Carolinites vizcainoi, may be a juvenile of C. genacinaca or C. tasmaniensis; its differences are consistent with ontogeny. A small number of specimens from Siberia and central China show differences in cranidial proportions from the Utah specimens that may be the result of preservational factors and/or photographic technique, or may represent genuine morphological disparity; this could be clarified if more specimens were to become available. This study suggests that C. genacinaca was ubiquitous in the epipelagic environment in a belt that encircled the planet between paleolatitudes of approximately 30°N and 30°S.

Exotic trilobites from the uppermost Cambrian Series 3 and lower Furongian of Sweden

“…They are morphologically comparable to the most widely distributed trilobite, the Ordovician Carolinites genacinaca Ross, 1951, which is considered to have been epipelagic (Fortey 1985;McCormick and Fortey 1999). Of the remaining exotic trilobite species from Scandinavia, none has morphological properties of the exoskeleton suggestive of a pelagic lifestyle, a point that was already brought up in the case of Maladioidella (e.g., Rushton and Hughes 1996).…”

Distribution of the order Proetida (Trilobita) in Baltoscandian Ordovician strata

“…The common palaeogeographical occurrence of Carolinites in the Ordovician tropical regions is explained by their epipelagic and active surface swimming lifestyle (Fortey 1975). Rare occurrences of this genus in higher latitudes, like in Baltica, and even farther towards the South Pole, in the Montagne Noire, France, and in Turkey, have been explained by gyres originating from the equatorial current that moved southwards (McCormick & Fortey 1999). An additional factor could be the Evae Drowning Event (see Nielsen 2004) (Fl2), supporting the widespread migration and arrival of new faunal elements.…”

“…The family Telephinidae is represented in the Lower Ordovician by Carolinites Kobayashi, the type species of which, C. genacinaca Ross, is the most widely distributed trilobite species known, according to McCormick & Fortey (1999). The broad palaeogeographical distribution of this genus is explained by its pelagic life style.…”

“…24. 4) and in South China Plate (Turvey & Zhou 2004), and is also known from Siberia, Australia, France (Montagne Noire), Turkey (see references in McCormick & Fortey 1999), and Iran (Bruton et al 2004).…”

Pelagic or benthic? Mode of life of the remopleuridid trilobite Hypodicranotus striatulus

“…During swimming, Hypodicranotus may depend on its eyes to determine its swimming direction and speed in response to ambient conditions. Therefore, the visual system should be adapted to faster swimming near the sea bottom because arthropods optimise their sensory traits in response to relevant adaptive strategies (e.g., Clarkson 1967Clarkson , 1975McCormick & Fortey 1999;Schoenemann et al 2010;Ono 2011). The strip-like visual surface of the eyes with many thousands of tiny lenses arranged in an almost vertical fashion (Whittington 1952) enables it to have lateral and forward view like other benthic trilobites and to see its surroundings in high resolution.…”