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Elrathia
Taxonomy
Elrathia was named by Walcott (1924).
It was assigned to Ptychoparioidea by Palmer (1954); to Ptychopariida by Sepkoski (2002); to Alokistocaridae by Briggs et al. (2008); and to Arthropoda by Caron and Jackson (2008).
It was assigned to Ptychoparioidea by Palmer (1954); to Ptychopariida by Sepkoski (2002); to Alokistocaridae by Briggs et al. (2008); and to Arthropoda by Caron and Jackson (2008).
Species
Species lacking formal opinion data
Synonymy list
| Year | Name and author |
|---|---|
| 1924 | Elrathia Walcott |
| 1954 | Elrathia Palmer p. 78 |
| 2002 | Elrathia Sepkoski |
| 2008 | Elrathia Briggs et al. p. 249 |
| 2008 | Elrathia Caron and Jackson p. 226 |
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
G. †Elrathia Walcott 1924
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†Elrathia grazierensis Rasetti 1965
†Elrathia idahoensis Resser 1938
†Elrathia kingi Meek 1870
†Elrathia longiceps Resser 1938
†Elrathia occidentalis Walcott 1884
†Elrathia permulta Walcott 1918
†Elrathia rara Resser 1939
†Elrathia sampsoni Resser 1938
†Elrathia spencei Resser 1939
Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| A. R. Palmer 1954 | Carapace elongate subovate in outline, widest at posterior margin of cephalon.
Cephalon subsemicircular in outline, genal angles extended into genal spines. Cranidium with anterior margin gently and evenly rounded. Glabella well defined by shallow dorsal furrow, straight sided, tapered forward, strongly and evenly rounded anteriorly. Glabellar furrows shallow or absent. Occipital furrow deepest at sides, shallow on midline. Occipital ring flat or gently arched, un- spined. Frontal area with distinct brim and border; border flat or gently arched upward; marginal furrow shallow. Width of fixed cheeks one-half or more width of glabella. Paipebral lobes opposite middle third of glabella, well defined by shallow palpebral furrow. Ocular ridges indistinct. Length of posterior limbs about equal to width of glabella at occipital furrow. Marginal furrow broad, shallow. Facial sutures diver- gent anterior and posterior to paipebral lobs; anterior course turns inward after reaching border and cuts margin about midway between anterolateral corners of cranidium and axial line; posterior course cuts margin before reaching genal spine. Free cheek with evenly curved lateral margin. Border well defined by shallow marginal furrow; ex- tended into short genal spine. Thorax of 13 segments. Axial lobe prominent; width less than half that of pleural lobes. Pleural lobe of each segment subequally divided by deep pleural fur- row; distal extremity extended into short, sharp point. Pygidium subsemicircular in outline, smaller than cephalon; axial length less than one-half width. Axial lobe prominent, not reaching posterior margin; width about one-half that of pleural lobes. Narrow border present, poorly defined by shallow marginal furrow. Furrows on axial and pleural lobes shallow. Surface of carapace smooth. |