Macraster washitae Lambert, 1920
Plate: MaWa-10
Series: Lower Cretaceous Group: Washita Formation: Duck Creek
Locale: Fink County: Grayson Stage: Albian
Length: 52.1 mm Width: 47.7 mm Height: 28.9 mm
Specimen in photos: BEG 21267 Holotype
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: BEG 21267 (Adkins Collection).
Locality: Fink, Grayson County, Texas.
Stratigraphy: Duck Creek Formation, 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 washitae Lambert, 1920
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
A Macraster characterized by a box-like, inflated profile with a truncated posterior end. Ambulacra are sunken, with the unpaired ambulacrum being narrower and deeper. Distinguished by the specific proportions of the petals and the angularity of the test (Lambert, 1920).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Duck Creek Formation; Fort Worth Limestone.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Grayson.
Abundance: Common in the lower Washita Group.
DESCRIPTION
TOP: Length, width, height: 52.1 mm L × 47.7 mm W × 28.9 mm H.
Top shape: Cordate with a very angular margin.
Top domed: Apex positioned at the posterior third (1/3 from posterior end).
SIDE: Ambitus: Positioned about 40% of height from the base.
Side shape: Almost box-like; sides inflated and curved.
Profile: Posterior end is vertically truncated; anterior end is sloping. From the ends, the test appears broad and bulbous.
BOTTOM: Bottom shape: Mostly flat.
AMB: Amb shape: All 5 ambulacra are sunken. The unpaired ambulacrum (III) is narrower and deeper than the paired ambulacra.
Amb arrangement: Paired ambulacra are wide, petaloid, and open at the outer ends.
Lengths: Anterior paired ambulacra are described as 25% longer than the posterior paired ambulacra.
Unpaired Amb: Pore pairs extend 80% of the distance to the margin.
INTERAMB: Shape: All interambulacra are slightly raised. A noticeable raised keel is present between the apical system and the posterior end.
PORE PAIRS: Shape: Pores in paired ambulacra are elongated. In the unpaired ambulacrum, pore pairs are elongated and arranged en chevron.
TUBERCLES: Primary Perforated: Yes.
Primary Crenulate: Yes.
Distribution: Tubercles and granulation cover most of the test; tubercles on the adoral surface are larger.
Mamelons: Broad.
Areolas: Sunken.
GRANULES: See Tubercles section.
FASCIOLE: None
APICAL SYSTEM: Size: Small.
Plating: Large madreporite.
PERIPROCT (ANUS): Shape: Small; longitudinally oval with pointed ends.
Location: Situated on the small truncated posterior end, about 1/3 up from the base.
Visibility: Barely visible from above.
PERISTOME (MOUTH): Shape: Subpentagonal.
Size: Depressed; about equal in size to the periproct.
Visibility: Barely visible from the anterior end.
Plastron: Large.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype BEG 21267.
ETYMOLOGY
Named for the Washita Group (and region) of Texas/Oklahoma.
REMARKS & COMPARISONS
Remarks: Lambert (1920) established this species for specimens previously identified as Hemiaster elegans by Clark (1915), arguing they differed from Shumard's type. Kamyabi Shadan et al. (2014) consider M. washitae to be a synonym of Macraster aguilerae (Böse, 1910), which they in turn often group with M. elegans. They suggest the variation in shape is environmental (ecophenotypic).
Comparisons:
Plate: MaWa-10
Series: Lower Cretaceous Group: Washita Formation: Duck Creek
Locale: Fink County: Grayson Stage: Albian
Length: 52.1 mm Width: 47.7 mm Height: 28.9 mm
Specimen in photos: BEG 21267 Holotype
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: BEG 21267 (Adkins Collection).
Locality: Fink, Grayson County, Texas.
Stratigraphy: Duck Creek Formation, Washita Group.
SYNONYMY
- Hemiaster elegans Clark, 1915 (partim) (non Shumard)
- Macraster elegans washitae (Lambert) Adkins, 1928
- Macraster aguilerae (Böse, 1910) (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 washitae Lambert, 1920
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
A Macraster characterized by a box-like, inflated profile with a truncated posterior end. Ambulacra are sunken, with the unpaired ambulacrum being narrower and deeper. Distinguished by the specific proportions of the petals and the angularity of the test (Lambert, 1920).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Duck Creek Formation; Fort Worth Limestone.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Grayson.
Abundance: Common in the lower Washita Group.
DESCRIPTION
TOP: Length, width, height: 52.1 mm L × 47.7 mm W × 28.9 mm H.
Top shape: Cordate with a very angular margin.
Top domed: Apex positioned at the posterior third (1/3 from posterior end).
SIDE: Ambitus: Positioned about 40% of height from the base.
Side shape: Almost box-like; sides inflated and curved.
Profile: Posterior end is vertically truncated; anterior end is sloping. From the ends, the test appears broad and bulbous.
BOTTOM: Bottom shape: Mostly flat.
AMB: Amb shape: All 5 ambulacra are sunken. The unpaired ambulacrum (III) is narrower and deeper than the paired ambulacra.
Amb arrangement: Paired ambulacra are wide, petaloid, and open at the outer ends.
Lengths: Anterior paired ambulacra are described as 25% longer than the posterior paired ambulacra.
Unpaired Amb: Pore pairs extend 80% of the distance to the margin.
INTERAMB: Shape: All interambulacra are slightly raised. A noticeable raised keel is present between the apical system and the posterior end.
PORE PAIRS: Shape: Pores in paired ambulacra are elongated. In the unpaired ambulacrum, pore pairs are elongated and arranged en chevron.
TUBERCLES: Primary Perforated: Yes.
Primary Crenulate: Yes.
Distribution: Tubercles and granulation cover most of the test; tubercles on the adoral surface are larger.
Mamelons: Broad.
Areolas: Sunken.
GRANULES: See Tubercles section.
FASCIOLE: None
APICAL SYSTEM: Size: Small.
Plating: Large madreporite.
PERIPROCT (ANUS): Shape: Small; longitudinally oval with pointed ends.
Location: Situated on the small truncated posterior end, about 1/3 up from the base.
Visibility: Barely visible from above.
PERISTOME (MOUTH): Shape: Subpentagonal.
Size: Depressed; about equal in size to the periproct.
Visibility: Barely visible from the anterior end.
Plastron: Large.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype BEG 21267.
ETYMOLOGY
Named for the Washita Group (and region) of Texas/Oklahoma.
REMARKS & COMPARISONS
Remarks: Lambert (1920) established this species for specimens previously identified as Hemiaster elegans by Clark (1915), arguing they differed from Shumard's type. Kamyabi Shadan et al. (2014) consider M. washitae to be a synonym of Macraster aguilerae (Böse, 1910), which they in turn often group with M. elegans. They suggest the variation in shape is environmental (ecophenotypic).
Comparisons:
- M. elegans: M. washitae is typically distinguished by its more angular, box-like profile compared to the more rounded or variably inflated M. elegans.
