Orthopsis charltoni (Cragin, 1894)
Plate: OrCh-10
Series: Upper Cretaceous Group: Washita Formation: Main Street Limestone
Locale: Denison County: Grayson Stage: Canomanian
Length: 25.0 mm Height: 11.3 mm
Specimen in photos: U.S.N.M. 32682 Holotype
Collector: Cragin/Taff
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
HOLOTYPE INFO:
Holotype: USNM 32682 (Cragin, 1894).
Locality: South of the Denison-Bonham road, near the lime-kiln about a mile east of Denison, Grayson County, Texas.
Stratigraphy: Choctaw Limestone (equivalent to the Main Street Limestone), Washita Group.
SYNONYMY
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Carinacea Kroh & Smith, 2010
Superorder: Echinacea Claus, 1876
Order: Orthopsida Mortensen, 1942
Family: Orthopsidae Duncan, 1889
Genus: ORTHOPSIS Cotteau, 1864
Species: Orthopsis charltoni (Cragin, 1894)
TYPE SPECIES: Cidaris miliaris d'Archiac, 1835
DIAGNOSIS
Test small, round-pentagonal, and arched above. Ambulacra are straight with simple, oblique pore pairs. Interambulacra possess six rows of primary tubercles, with the middle row in each half-area being the largest. Surface closely granulated (Cragin, 1894).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Main Street Limestone (historically "Choctaw Limestone").
Stratigraphic Units: Upper Cretaceous, Cenomanian.
Counties: Grayson.
Abundance: Rare.
Associated Fauna: Exogyra arietina, Ostrea quadruplicata, Lima wacoensis (Cragin, 1894).
DESCRIPTION
TOP: Length, width, height: 25.0 mm L × 25.0 mm W × 11.3 mm H.
Top shape: Round-pentagonal (Cragin, 1894).
Top domed: Arched above.
SIDE: Side shape: Inflated.
BOTTOM: Bottom shape: Concave below (Cragin, 1894).
AMB: Amb shape: Half as broad as the interambulacra.
Amb arrangement: Each ambulacrum is ornamented with two rows of primary tubercles that are somewhat smaller than the largest interambulacral tubercles.
Plating: Each primary tubercle is subtended by an irregularly polygonal string of smaller secondary tubercles (Cragin, 1894).
PORE PAIRS: Shape: Pores somewhat elongated in the direction of the belt.
Arrangement: Pore belts straight; pore pairs simple (uniserial) throughout and somewhat oblique (Cragin, 1894).
TUBERCLES: Primary Perforated: Yes.
Primary Crenulate: No (Non-crenulated) (Cragin, 1894).
Interambulacral Tubercles: Six rows of primary tubercles; the middle row of each semi-ambulacrum (half-plate) is much larger than the others.
Arrangement: Primaries are subtended by secondaries, mostly in polygonal strings (Cragin, 1894).
GRANULES: Distribution: Surface of test closely granulated in the intervals between tubercles (Cragin, 1894).
FASCIOLE: Absent.
APICAL SYSTEM: Size: Moderately broad (Cragin, 1894).
PERIPROCT (ANUS): Size: Moderately broad; greatest breadth 3.5 mm.
PERISTOME (MOUTH): Size: Breadth about 7 or 8 mm (Cragin, 1894).
Comparisons: Considerably smaller in proportion to the test than in Loriolia texana (Pseudodiadema texanum), but proportionately larger than in Orthopsis casanovai (Cooke, 1955).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype USNM 32682.
ETYMOLOGY
Named in honor of Professor O. C. Charlton, a friend and fellow traveler of the author (Cragin, 1894).
REMARKS & COMPARISONS
Remarks: Cragin (1894) originally assigned this species to Hemipedina but noted that it possessed "perforated and non-crenulated tubercles," which is the diagnostic character of the genus Orthopsis (Hemipedina has crenulate tubercles). Clark (1915) later formally moved the species to Orthopsis.
Comparisons:
Plate: OrCh-10
Series: Upper Cretaceous Group: Washita Formation: Main Street Limestone
Locale: Denison County: Grayson Stage: Canomanian
Length: 25.0 mm Height: 11.3 mm
Specimen in photos: U.S.N.M. 32682 Holotype
Collector: Cragin/Taff
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
HOLOTYPE INFO:
Holotype: USNM 32682 (Cragin, 1894).
Locality: South of the Denison-Bonham road, near the lime-kiln about a mile east of Denison, Grayson County, Texas.
Stratigraphy: Choctaw Limestone (equivalent to the Main Street Limestone), Washita Group.
SYNONYMY
- Hemipedina charltoni Cragin, 1894
- Orthopsis charltoni (Cragin) Clark, 1915
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Carinacea Kroh & Smith, 2010
Superorder: Echinacea Claus, 1876
Order: Orthopsida Mortensen, 1942
Family: Orthopsidae Duncan, 1889
Genus: ORTHOPSIS Cotteau, 1864
Species: Orthopsis charltoni (Cragin, 1894)
TYPE SPECIES: Cidaris miliaris d'Archiac, 1835
DIAGNOSIS
Test small, round-pentagonal, and arched above. Ambulacra are straight with simple, oblique pore pairs. Interambulacra possess six rows of primary tubercles, with the middle row in each half-area being the largest. Surface closely granulated (Cragin, 1894).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Main Street Limestone (historically "Choctaw Limestone").
Stratigraphic Units: Upper Cretaceous, Cenomanian.
Counties: Grayson.
Abundance: Rare.
Associated Fauna: Exogyra arietina, Ostrea quadruplicata, Lima wacoensis (Cragin, 1894).
DESCRIPTION
TOP: Length, width, height: 25.0 mm L × 25.0 mm W × 11.3 mm H.
Top shape: Round-pentagonal (Cragin, 1894).
Top domed: Arched above.
SIDE: Side shape: Inflated.
BOTTOM: Bottom shape: Concave below (Cragin, 1894).
AMB: Amb shape: Half as broad as the interambulacra.
Amb arrangement: Each ambulacrum is ornamented with two rows of primary tubercles that are somewhat smaller than the largest interambulacral tubercles.
Plating: Each primary tubercle is subtended by an irregularly polygonal string of smaller secondary tubercles (Cragin, 1894).
PORE PAIRS: Shape: Pores somewhat elongated in the direction of the belt.
Arrangement: Pore belts straight; pore pairs simple (uniserial) throughout and somewhat oblique (Cragin, 1894).
TUBERCLES: Primary Perforated: Yes.
Primary Crenulate: No (Non-crenulated) (Cragin, 1894).
Interambulacral Tubercles: Six rows of primary tubercles; the middle row of each semi-ambulacrum (half-plate) is much larger than the others.
Arrangement: Primaries are subtended by secondaries, mostly in polygonal strings (Cragin, 1894).
GRANULES: Distribution: Surface of test closely granulated in the intervals between tubercles (Cragin, 1894).
FASCIOLE: Absent.
APICAL SYSTEM: Size: Moderately broad (Cragin, 1894).
PERIPROCT (ANUS): Size: Moderately broad; greatest breadth 3.5 mm.
PERISTOME (MOUTH): Size: Breadth about 7 or 8 mm (Cragin, 1894).
Comparisons: Considerably smaller in proportion to the test than in Loriolia texana (Pseudodiadema texanum), but proportionately larger than in Orthopsis casanovai (Cooke, 1955).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype USNM 32682.
ETYMOLOGY
Named in honor of Professor O. C. Charlton, a friend and fellow traveler of the author (Cragin, 1894).
REMARKS & COMPARISONS
Remarks: Cragin (1894) originally assigned this species to Hemipedina but noted that it possessed "perforated and non-crenulated tubercles," which is the diagnostic character of the genus Orthopsis (Hemipedina has crenulate tubercles). Clark (1915) later formally moved the species to Orthopsis.
Comparisons:
- Orthopsis casanovai: Cooke (1955) noted that the peristome of O. casanovai is proportionately much smaller than that of O. charltoni.
- Orthopsis occidentalis: Cragin noted similarities to O. occidentalis (Cragin, 1893) from the Trinity Group but distinguished them by stratigraphic level and tubercular arrangement.
