Macraster kentensis Adkins, 1930
Plate: MaKe-10
Series: Lower Cretaceous Group: Washita Formation: Duck Creek
Locale: Denison County: Grayson Stage: Albian
Length: 56.6 mm Width:52.1 mm Height:34.3 mm
Specimen in photos: Collection of Ed Elliott
Repository: Private Collection
HOLOTYPE INFO:
Holotype: UT 1734 (BEG/NPL) (Adkins, 1930).
Locality: 2 miles north of Kent, Culberson County, Texas.
Stratigraphy: Upper Fort Worth Limestone, Washita Group.
SYNONYMY
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata Zittel, 1879
Order: Spatangoida L. Agassiz, 1840
Family: Macrasteridae Lambert, 1920
Genus: MACRASTER Roemer, 1888
Species: Macraster kentensis Adkins, 1930
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
Test tall and inflated with a distinct posterior keel. Characterized by narrow, lanceolate paired ambulacra and a narrow anterior sulcus. The posterior face is truncated, creating a protrusion (Adkins, 1930).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Duck Creek Formation (Specimen); Fort Worth Limestone (Type).
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Grayson (Specimen); Culberson (Type).
Abundance: Rare.
DESCRIPTION
TOP: Length, width, height: 56.6 mm L × 52.1 mm W × 34.3 mm H.
Top shape: Cordate. A noticeable raised keel is present between the apical system and the posterior margin.
Top domed: Very inflated. Apex is positioned slightly posterior of the midpoint.
SIDE: Ambitus: Positioned low, approximately 1/3 from the base.
Side shape: Posterior end is truncated away from the test, creating a protrusion. Anterior end has a narrow sulcus.
BOTTOM: Bottom shape: Flat with a slight slope.
AMB: Amb shape: All five ambulacra are slightly sunken. Paired ambulacra are narrow, lanceolate, and open at the outer ends.
Amb arrangement: Both sets of paired ambulacra are equal in length, with the posterior pair reaching the margin.
Unpaired Amb: Pore pairs are elongated and arranged en chevron (typical of Macraster). Pores become wider spaced as the distance from the apical disc increases and continue onto the adoral surface.
INTERAMB: Shape: All interambulacra are slightly raised from the surface. A keel is prominent in the posterior interambulacrum.
PORE PAIRS: Shape: Elongated and close together in the paired ambulacra.
TUBERCLES: Distribution: Sparse; slightly more plentiful on the adoral surface.
GRANULES: Distribution: Sparse.
FASCIOLE: Absent in Macraster.
APICAL SYSTEM: Size: Small.
Genital pores: 4 gonopores
PERIPROCT (ANUS): Shape: Very small; longitudinally oval.
Location: Situated on the small truncated posterior end, about at the midpoint from the base.
Visibility: Cannot be seen from above.
PERISTOME (MOUTH): Shape: Transversely subpentagonal.
Size: Depressed; about equal in size to the periproct.
Visibility: Clearly visible from the anterior end; protruding.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied from the Collection of Ed Elliott.
ETYMOLOGY
Named for the town of Kent, Culberson County, Texas, near the type locality (Adkins, 1930).
REMARKS & COMPARISONS
Remarks: Kamyabi Shadan et al. (2014) regard M. kentensis as a synonym of Macraster elegans (Shumard, 1853), noting that the proliferation of species names for large, inflated Macraster in the USA and Mexico is likely an overestimation of diversity based on local ecophenotypic variants.
Comparisons:
Plate: MaKe-10
Series: Lower Cretaceous Group: Washita Formation: Duck Creek
Locale: Denison County: Grayson Stage: Albian
Length: 56.6 mm Width:52.1 mm Height:34.3 mm
Specimen in photos: Collection of Ed Elliott
Repository: Private Collection
HOLOTYPE INFO:
Holotype: UT 1734 (BEG/NPL) (Adkins, 1930).
Locality: 2 miles north of Kent, Culberson County, Texas.
Stratigraphy: Upper Fort Worth Limestone, Washita Group.
SYNONYMY
- Macraster elegans (Shumard, 1853) (fide Kamyabi Shadan et al., 2014)
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata Zittel, 1879
Order: Spatangoida L. Agassiz, 1840
Family: Macrasteridae Lambert, 1920
Genus: MACRASTER Roemer, 1888
Species: Macraster kentensis Adkins, 1930
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
Test tall and inflated with a distinct posterior keel. Characterized by narrow, lanceolate paired ambulacra and a narrow anterior sulcus. The posterior face is truncated, creating a protrusion (Adkins, 1930).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Duck Creek Formation (Specimen); Fort Worth Limestone (Type).
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Grayson (Specimen); Culberson (Type).
Abundance: Rare.
DESCRIPTION
TOP: Length, width, height: 56.6 mm L × 52.1 mm W × 34.3 mm H.
Top shape: Cordate. A noticeable raised keel is present between the apical system and the posterior margin.
Top domed: Very inflated. Apex is positioned slightly posterior of the midpoint.
SIDE: Ambitus: Positioned low, approximately 1/3 from the base.
Side shape: Posterior end is truncated away from the test, creating a protrusion. Anterior end has a narrow sulcus.
BOTTOM: Bottom shape: Flat with a slight slope.
AMB: Amb shape: All five ambulacra are slightly sunken. Paired ambulacra are narrow, lanceolate, and open at the outer ends.
Amb arrangement: Both sets of paired ambulacra are equal in length, with the posterior pair reaching the margin.
Unpaired Amb: Pore pairs are elongated and arranged en chevron (typical of Macraster). Pores become wider spaced as the distance from the apical disc increases and continue onto the adoral surface.
INTERAMB: Shape: All interambulacra are slightly raised from the surface. A keel is prominent in the posterior interambulacrum.
PORE PAIRS: Shape: Elongated and close together in the paired ambulacra.
TUBERCLES: Distribution: Sparse; slightly more plentiful on the adoral surface.
GRANULES: Distribution: Sparse.
FASCIOLE: Absent in Macraster.
APICAL SYSTEM: Size: Small.
Genital pores: 4 gonopores
PERIPROCT (ANUS): Shape: Very small; longitudinally oval.
Location: Situated on the small truncated posterior end, about at the midpoint from the base.
Visibility: Cannot be seen from above.
PERISTOME (MOUTH): Shape: Transversely subpentagonal.
Size: Depressed; about equal in size to the periproct.
Visibility: Clearly visible from the anterior end; protruding.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied from the Collection of Ed Elliott.
ETYMOLOGY
Named for the town of Kent, Culberson County, Texas, near the type locality (Adkins, 1930).
REMARKS & COMPARISONS
Remarks: Kamyabi Shadan et al. (2014) regard M. kentensis as a synonym of Macraster elegans (Shumard, 1853), noting that the proliferation of species names for large, inflated Macraster in the USA and Mexico is likely an overestimation of diversity based on local ecophenotypic variants.
Comparisons:
- M. elegans: M. kentensis was originally distinguished by Adkins based on its taller profile, specific ambulacral dimensions, and stratigraphic position (Fort Worth Limestone).
