Diplograptus amplexicaulis Graptolite and Cryptolithoides ulrichi Trilobite on matrix a.jpg
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Diplograptus amplexicaulis Graptolite & Cryptolithoides ulrichi Trilobite on matrix
SITE LOCATION: Viola Limestone, Murray County, Oklahoma, USA
TIME PERIOD: Ordovician Period (445-485 Million Years ago)
Data: Diplograptus was a Cambrian genus of graptolites. Graptolithina is a class of hemichordate animal, the members of which are known as graptolites. Graptolites are colonial animals known chiefly as fossils from the Middle Cambrian (Series 3, Stage 5) through the Lower Carboniferous (Mississippian). The name graptolite comes from the Greek graptos, meaning "written", and lithos, meaning "rock", as many graptolite fossils resemble hieroglyphs written on the rock. Linnaeus originally regarded them as 'pictures resembling fossils' rather than true fossils, though later workers supposed them to be related to the hydrozoans. Since the 1970s, as a result of advances in electron microscopy, graptolites have generally been thought to be most closely allied to the pterobranchs, a rare group of modern marine animals belonging to the phylum Hemichordata (hemichordates). Comparisons are drawn with the modern hemichordates Cephalodiscus and Rhabdopleura. Graptolites are common fossils and have a worldwide distribution. The preservation, quantity and gradual change over a geologic time scale of graptolites allows the fossils to be used to date strata of rocks throughout the world. Trinucleidae is a family of small to average size asaphid trilobites that first occurred at the start of the Ordovician and became extinct at the end of that period. It contains approximately 227 species divided over 51 genera in 5 subfamilies. The most conspicuous character is the wide perforated fringe of the head. Trinucleids have a relatively large headshield, that is characterized by a highly vaulted pear-shaped glabella, separated by deep furrows from the cheeks that are often vaulted too, but less so. To the front and sides of this tri-nucleate centre is a wide seam (or fringe), that often inclinates towards the outer margin, and is perforated by funnel shaped pits. These pits are only in one row at the front in the first occurring genera, irregularly distributed in early species, but in later species these are largely arranged in several rows parallel to the margin, and in arches more or less perpendicular to the margin. The thorax consists of six short but wide segments, the outline of which is a continuation of the cheeks. The axis is narrow, less than ?× as wide as each of the ribs (or pleurae) to its sides. The tailshield, termed pygidium, is small, approximately wide triangular, with the axis narrow triangular, reaching the border. The axial rings and ribs become less conspicuous further to the back. Trinucleids lived in deeper water. At first, the pits in the fringe were considered to have a sensory function, but the suggestion that they may play a role in filtering food particles now seems generally accepted. Taxonomy is split - Graptolite first, trilobite second.
Kingdom: Animalia/Animalia
Phylum: Hemichordata/Arthropoda
Class: †Graptolithina/†Trilobita
Order: †Graptoloidea/†Asaphida
Family: †Diplograptidae/†Trinucleidae
Genus: †Diplograptus/†Cryptolithoides
Species: †amplexicaulis/†ulrichi
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