''Dalmanites'' is a genus of

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

in the order

Phacopida Phacopida ("lens-face") is an order of trilobites that lived from the Late Cambrian to the Late Devonian. It is made up of a morphologically diverse assemblage of taxa in three related suborders. Characteristics Phacopida had 8 to 19 thoraci ...

. They lived from the

Late Ordovician The Late Ordovician is the third and final epoch of the Ordovician period, lasting million years and spanning from around 458.2 to 443.1 million years ago. The rocks associated with this epoch are referred to as the Upper Ordovician Series. At ...

Middle Devonian In the geological timescale, the Middle Devonian epoch (from 393.3 ± 1.2 million years ago to 382.7 ± 1.6 million years ago) occurred during the Devonian period, after the end of the Emsian age. The Middle Devonian epoch is subdivided into two ...

. The trilobites of this genus have slightly convex

exoskeleton An exoskeleton () . is a skeleton that is on the exterior of an animal in the form of hardened integument, which both supports the body's shape and protects the internal organs, in contrast to an internal endoskeleton (e.g. human skeleton, that ...

s with an average length of . The

cephalon Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino Jr., Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont ...

is semicircular or parabolic. The

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior ...

(center portion of the head) is often pear-shaped, and tapers outward toward the front. The glabella also always contains three pairs of obvious glabellar furrows. Also prominent are the large mosaic (schizochroal) eyes. The thorax is composed of eleven segments, with the relatively large

pygidium The pygidium (: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compos ...

with a slender axis of 11 to 16 rings and 6 or 7 pleural ribs. The pygidium ends in a striking tail spike.

Taxonomy

Species previously assigned to ''Dalmanites''

Some species formerly included in ''Dalmanites'' have now been reassigned to other genera. * ''D. lapeyrei'' = '' Zeliszkella torrubiae'' * ''D. maecurua'' = ''Amazonaspis maecurua'' * ''D. micheli'' = '' Phacopidina micheli'' * ''D. pleione'' = '' Bellacartwrightia pleione'' * ''D. torrubiae'' = '' Zeliszkella torrubiae'' * ''D. weaveri var. tenuimucronata'' = '' Bessazoon tenuimucronata''

Description

''Dalmanites'' is genus of

s with an average (about long), moderately vaulted

with an inverted egg-shaped outline (about 1.5× longer than wide). Its headshield (or

) is semicircular, with robust (genal) spines extending from the side of the cephalon back to approximately the 8th

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...

segment. The frontal margin of the cephalon is semicircular to parabolic, and it may have a simple and short anterior extension. The facial suture lies inside or touches the preglabellar furrow. The frontal lobe of the central raised area of the cephalon (or

) is much wider than the other lobes. The frontal lobe is vaulted. The eye is moderate to large, about half as long as the cheek. The "seem" that is visible from the

ventral Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

side (or doublure) is wide and flat, and has a deep and wide antennal furrow. The "palate" (or hypostome), also only visible from the ventral side, is subtriangular (about as long as wide) and adorned with three weak denticles at its back rim. To the front the hypostome has weak wings extending sideways. The thorax consists of 11 segments. The tips of the segments are pointed and angle back increasingly from about 30° for the anterior segment to slightly pointing inwards for the posterior segment. The tailshield (or

) is large, subtriangular, and about two-thirds to three-fourths as long as wide. The axis is vaulted and ±35% of the width of the pygidium and consists of 12-15 rings. 9–10 deep and wide pleural furrows have flat or only slightly concave bottoms. The furrows within each pleural rib (or interpleural furrows) are very narrow. The frontal band of each pleural rib is more vaulted and broader than the rear band. The pleural furrows almost reach the margin. The pygidial termination (or mucro) is vaulted and more or less pointed into a spine, which may differ between species. The entire exoskeleton is covered in fine and coarse granules. A specimen of an indeterminate species with preserved soft tissue is known from the Silurian aged

Coalbrookdale Formation Coalbrookdale Formation, earlier known as Wenlock Shale or Wenlock Shale Formation and also referred to as Herefordshire Lagerstätte in palaeontology, is a fossil-rich deposit ('' Konservat-Lagerstätte'') in Powys and Herefordshire at the Engl ...

of England. The antennae are not preserved, though biramous limb pairs are preserved, three are present on the cephalon, 11 on the thorax and at least 3 on the pygidium. The thoracic pairs become smaller posteriorly. The exopods of the limbs bear filamentous structures, which appear to be joined with each other by a membrane.

References

{{Taxonbar, from=Q3701172 Dalmanitidae Ordovician trilobites Silurian trilobites Devonian trilobites Trilobites of North America Devonian trilobites of South America Devonian Colombia Fossils of Colombia Late Ordovician first appearances Middle Devonian genus extinctions Fossil taxa described in 1852 Jeffersonville Limestone Paleozoic life of Ontario Floresta Formation Paleozoic life of New Brunswick Paleozoic life of Nova Scotia Paleozoic life of Quebec Taxa named by Joachim Barrande Phacopida genera