The megalograptids were likely the first major successful group of eurypterids, evidenced by a Late Ordovician radiation. All known members of the Megalograptidea are from the Late Ordovician of Laurentia[1] with the exception of the large Pentecopterus from the Middle Ordovician.
Megalograptids are characterized by large exoskeletons with ovate to triangular scales. The prosoma (head) is subquadrate, with a tonguelike anterior process bearing marginal spines, and compound eyes on the top front of the head. The chelicerae (claws in front of the mouth) are small and short. The first and third pairs of walking legs are short, with diverging or closely spaced spines. The second pair of walking legs is enormously developed, with long paired spines. The fourth pair of walking legs are nearly spineless. The preabdomen, the front portion of the body, is narrow with axial furrows, while the postabdomen is moderately narrow with broad, flat and curved appendages on the last body segment. The telson is short and lanceolate.[2]
Classificationedit
The Megalograptidae are thought to be relatively primitive (between the genus Onychopterella and the Eurypteroidea) because they lack the synapomorphy of all more derived swimming eurypterines, the modified distal margin of the sixth podomere of the swimming leg. Though such a position has never been recovered in phylogenetic analyses and is primarily based on the lack of said characteristic and other traits that are thought to be primitive. The clade might instead belong between the Eurypteroidea and the Mixopteroidea since the sixth podomere in the swimming leg resembles the reduced podomere found in the Mixopteridae.[1]
Generaedit
Family Megalograptidae Caster & Kjellesvig-Waering, 1955
megalograptidae, family, eurypterids, extinct, group, chelicerate, arthropods, commonly, known, scorpions, temporal, range, middle, ordovician, late, ordovician, preꞒ, nmegalograptusscientific, classificationdomain, eukaryotakingdom, animaliaphylum, arthropoda. Megalograptidae are a family of eurypterids an extinct group of chelicerate arthropods commonly known as sea scorpions MegalograptidaeTemporal range Middle Ordovician Late Ordovician 467 3 443 8 Ma PreꞒ Ꞓ O S D C P T J K Pg NMegalograptusScientific classificationDomain EukaryotaKingdom AnimaliaPhylum ArthropodaSubphylum ChelicerataOrder EurypteridaInfraorder DiploperculataSuperfamily CarcinosomatoideaFamily MegalograptidaeCaster amp Kjellesvig Waering 1955GeneraMegalograptus Echinognathus PentecopterusThe megalograptids were likely the first major successful group of eurypterids evidenced by a Late Ordovician radiation All known members of the Megalograptidea are from the Late Ordovician of Laurentia 1 with the exception of the large Pentecopterus from the Middle Ordovician Contents 1 Description 2 Classification 3 Genera 4 See also 5 ReferencesDescription editMegalograptids are characterized by large exoskeletons with ovate to triangular scales The prosoma head is subquadrate with a tonguelike anterior process bearing marginal spines and compound eyes on the top front of the head The chelicerae claws in front of the mouth are small and short The first and third pairs of walking legs are short with diverging or closely spaced spines The second pair of walking legs is enormously developed with long paired spines The fourth pair of walking legs are nearly spineless The preabdomen the front portion of the body is narrow with axial furrows while the postabdomen is moderately narrow with broad flat and curved appendages on the last body segment The telson is short and lanceolate 2 Classification editThe Megalograptidae are thought to be relatively primitive between the genus Onychopterella and the Eurypteroidea because they lack the synapomorphy of all more derived swimming eurypterines the modified distal margin of the sixth podomere of the swimming leg Though such a position has never been recovered in phylogenetic analyses and is primarily based on the lack of said characteristic and other traits that are thought to be primitive The clade might instead belong between the Eurypteroidea and the Mixopteroidea since the sixth podomere in the swimming leg resembles the reduced podomere found in the Mixopteridae 1 Genera editFamily Megalograptidae Caster amp Kjellesvig Waering 1955 Megalograptus Miller 1874 Echinognathus Walcott 1882 Pentecopterus Lamsdell et al 2015See also edit nbsp Paleontology portalList of eurypteridsReferences edit a b O Erik Tetlie 2007 Distribution and dispersal history of Eurypterida Chelicerata PDF Palaeogeography Palaeoclimatology Palaeoecology 252 3 4 557 574 doi 10 1016 j palaeo 2007 05 011 Archived from the original PDF on 2011 07 18 Stormer L 1955 Merostomata Treatise on Invertebrate Paleontology Part P Arthropoda 2 Chelicerata P36 nbsp This eurypterid related article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Megalograptidae amp oldid 1040560010, wikipedia, wiki, book, books, library,
