Macraster elegans washitae (Lambert, 1920)
Plate: MaeWa-10
Series: Lower Cretaceous Group: Washita Formation: Duck Creek
Locale: County: Grayson Stage: Albian
Length: 38.6 mm Width: 36.1 mm Height: 24.8 mm
Specimen in photos: U.S.N.M. 304188 Hypotype
Repository: Paleobiology Dept., NMNH, Smithsonian Institution Red Ink
HOLOTYPE INFO:
Holotype: Originally described by Lambert (1920). Repository likely MNHN (Paris).
Locality: Fort Worth or Denison, Texas.
Stratigraphy: Washita Group (Duck Creek or Fort Worth Limestone).
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 elegans (Shumard, 1853)
Subspecies: Macraster elegans washitae (Lambert, 1920)
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
A subspecies of Macraster elegans characterized by a smaller, cordate test with a wide posterior. The paired ambulacra are wide, lanceolate, and petaloid. Distinguished from the typical form by minor variations in inflation and ambulacral width, often considered a synonym of M. elegans.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Duck Creek Formation.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Grayson.
Abundance: Common in the lower Washita Group.
DESCRIPTION
TOP: Length, width, height: 38.6 mm L × 36.1 mm W × 24.8 mm H.
Top shape: Cordate; angular anterior, narrowing to a wide posterior.
Top domed: Apex situated just slightly posterior of the midpoint.
SIDE: Ambitus: Positioned about 45% from the bottom.
Side shape: Very inflated; sides curved.
Profile: Posterior end is tall and vertically truncated; anterior end is narrower and sloping.
BOTTOM: Bottom shape: Curved.
AMB: Amb shape: All paired ambulacra are slightly depressed, wide, lanceolate, and petaloid. Ends are open. Posterior pair is slightly flexuous.
Amb arrangement: Paired ambulacra are about equal in length with the posterior pair.
INTERAMB: Not specified.
PORE PAIRS: Arrangement: Unpaired ambulacrum pores are arranged en chevron (distinctive for Macraster).
Shape: Pore pairs in paired ambulacra are elongated.
TUBERCLES: Primary Perforated: Yes.
Primary Crenulate: Yes (pronounced).
Distribution: Large tubercles present.
GRANULES: Distribution: Granulation is even over most of the test.
FASCIOLE: Absent in Macraster.
APICAL SYSTEM: Size: Small.
Genital pores: 4 gonopores.
Plating: Small madreporite.
PERIPROCT (ANUS): Shape: Longitudinally oval with pointed ends; small.
Location: Situated above the midpoint on the posterior truncation.
Visibility: Barely visible from above.
PERISTOME (MOUTH): Shape: Transversely subpentagonal.
Size: Smaller than the periproct.
Visibility: Visible from the posterior end.
Plastron: Large.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype USNM 304188. Note on label: "Red Ink."
ETYMOLOGY
Named for the Washita Group of Texas, from which the type material was collected.
REMARKS & COMPARISONS
Remarks: Lambert (1920) originally distinguished M. washitae based on ambulacral width and profile. However, Kamyabi Shadan et al. (2014) reviewed the genus and concluded that M. elegans washitae is a synonym of Macraster elegans (Shumard, 1853), stating that the high number of species names given for large, inflated Macraster in the USA and Mexico is overestimated and likely represents ecophenotypic variation (local variants described as species). Cooke (1946) also noted that M. denisonensis might be a synonym of this form.
Plate: MaeWa-10
Series: Lower Cretaceous Group: Washita Formation: Duck Creek
Locale: County: Grayson Stage: Albian
Length: 38.6 mm Width: 36.1 mm Height: 24.8 mm
Specimen in photos: U.S.N.M. 304188 Hypotype
Repository: Paleobiology Dept., NMNH, Smithsonian Institution Red Ink
HOLOTYPE INFO:
Holotype: Originally described by Lambert (1920). Repository likely MNHN (Paris).
Locality: Fort Worth or Denison, Texas.
Stratigraphy: Washita Group (Duck Creek or Fort Worth Limestone).
SYNONYMY
- Macraster washitae Lambert, 1920
- 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 elegans (Shumard, 1853)
Subspecies: Macraster elegans washitae (Lambert, 1920)
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
A subspecies of Macraster elegans characterized by a smaller, cordate test with a wide posterior. The paired ambulacra are wide, lanceolate, and petaloid. Distinguished from the typical form by minor variations in inflation and ambulacral width, often considered a synonym of M. elegans.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Duck Creek Formation.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Grayson.
Abundance: Common in the lower Washita Group.
DESCRIPTION
TOP: Length, width, height: 38.6 mm L × 36.1 mm W × 24.8 mm H.
Top shape: Cordate; angular anterior, narrowing to a wide posterior.
Top domed: Apex situated just slightly posterior of the midpoint.
SIDE: Ambitus: Positioned about 45% from the bottom.
Side shape: Very inflated; sides curved.
Profile: Posterior end is tall and vertically truncated; anterior end is narrower and sloping.
BOTTOM: Bottom shape: Curved.
AMB: Amb shape: All paired ambulacra are slightly depressed, wide, lanceolate, and petaloid. Ends are open. Posterior pair is slightly flexuous.
Amb arrangement: Paired ambulacra are about equal in length with the posterior pair.
INTERAMB: Not specified.
PORE PAIRS: Arrangement: Unpaired ambulacrum pores are arranged en chevron (distinctive for Macraster).
Shape: Pore pairs in paired ambulacra are elongated.
TUBERCLES: Primary Perforated: Yes.
Primary Crenulate: Yes (pronounced).
Distribution: Large tubercles present.
GRANULES: Distribution: Granulation is even over most of the test.
FASCIOLE: Absent in Macraster.
APICAL SYSTEM: Size: Small.
Genital pores: 4 gonopores.
Plating: Small madreporite.
PERIPROCT (ANUS): Shape: Longitudinally oval with pointed ends; small.
Location: Situated above the midpoint on the posterior truncation.
Visibility: Barely visible from above.
PERISTOME (MOUTH): Shape: Transversely subpentagonal.
Size: Smaller than the periproct.
Visibility: Visible from the posterior end.
Plastron: Large.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype USNM 304188. Note on label: "Red Ink."
ETYMOLOGY
Named for the Washita Group of Texas, from which the type material was collected.
REMARKS & COMPARISONS
Remarks: Lambert (1920) originally distinguished M. washitae based on ambulacral width and profile. However, Kamyabi Shadan et al. (2014) reviewed the genus and concluded that M. elegans washitae is a synonym of Macraster elegans (Shumard, 1853), stating that the high number of species names given for large, inflated Macraster in the USA and Mexico is overestimated and likely represents ecophenotypic variation (local variants described as species). Cooke (1946) also noted that M. denisonensis might be a synonym of this form.
