Macraster obesus Adkins, 1930
Plate: MaOb-10
Series: Lower Cretaceous Group: Washita Formation: Weno
Locale: Denton County: Grayson Stage: Albian
Length: 98.4 mm Width: 93.0 mm Height: 57.1 mm
Specimen in photos: U.S.N.M. 466603 Type
Paleobiology Depart. NMNH, Smithsonian Institution
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
HOLOTYPE INFO:
Holotype: USNM 466603 (Originally UT 996) (Adkins, 1930).
Locality: Fort Worth, Tarrant County, Texas (Adkins, 1930).
Stratigraphy: Weno 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 obesus Adkins, 1930
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
A very large Macraster distinguished by its "obese," highly inflated profile and high vertical sides. The test is cordate with a distinct anterior notch. Ambulacra are long, deeply sunken, and extend almost to the ambitus. Distinguished from M. elegans by its greater height relative to length and width (Adkins, 1930).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Weno Formation (Adkins, 1930); Fort Worth Limestone.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Grayson, Tarrant.
Abundance: Rare; typically found in the upper Washita Group.
DESCRIPTION
TOP: Length, width, height: 98.4 mm L × 93.0 mm W × 57.1 mm H.
Top shape: Cordate with a very angular margin. Pointed posteriorly.
Top domed: Very inflated; apex is located slightly posterior of the midpoint. Adkins (1930) notes the highest point is posterior to the apical system.
SIDE: Ambitus: Positioned approximately 38% from the base.
Side shape: Very inflated; "obese."
Profile: Anterior end is long and truncated; posterior end is sloping. From the ends, the test appears broad and very rounded.
BOTTOM: Bottom shape: Mostly flat, yet slightly curved/convex.
AMB: Amb shape: All 5 ambulacra are equally sunken.
Amb arrangement: Paired ambulacra are wide, lanceolate, slightly flexuous, and open at the outer ends. Anterior paired ambulacra are slightly longer than the posterior pair and almost reach the margin (Adkins, 1930).
Unpaired Amb: Narrower than the paired ambulacra.
PORE PAIRS: Arrangement: Unpaired ambulacrum pores are slightly elongated and arranged en chevron.
Shape: Pores in paired ambulacra are elongated.
TUBERCLES: Primary Perforated: Yes.
Primary Crenulate: Yes.
Distribution: Tubercles and granulation are mostly even over the entire test.
Areolas: Sunken.
INTERAMB: Shape: All 5 interambulacra are raised. The posterior interambulacrum features a large flattened surface.
GRANULES: Distribution: Evenly distributed.
FASCIOLE: Absent in Macraster).
APICAL SYSTEM: Size: Small.
Plating: Madreporite constitutes about 1/4 of the apical system.
Genital Pores: 4 gonopores (Adkins, 1930).
PERIPROCT (ANUS): Shape: Small; longitudinally oval with both ends pointed.
Location: Situated slightly above the midpoint.
Visibility: Barely visible from above.
PERISTOME (MOUTH): Shape: Subpentagonal; wide.
Size: Depressed; about equal in size to the periproct.
Location: Located about 25% from the anterior margin.
Visibility: Cannot be seen from the anterior end.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype USNM 466603 (Specimen in photos).
ETYMOLOGY
From the Latin obesus (fat, stout, plump), referring to the highly inflated profile of the test (Adkins, 1930).
REMARKS & COMPARISONS
Remarks: Adkins (1930) described M. obesus as having a "very tall, inflated test" differing from M. elegans by its proportions. However, Kamyabi Shadan et al. (2014) regard M. obesus as a synonym of Macraster elegans (Shumard, 1853), stating that the high number of species names for large, inflated Macraster in North America is an overestimation based on local ecophenotypic variants.
Comparisons:
Plate: MaOb-10
Series: Lower Cretaceous Group: Washita Formation: Weno
Locale: Denton County: Grayson Stage: Albian
Length: 98.4 mm Width: 93.0 mm Height: 57.1 mm
Specimen in photos: U.S.N.M. 466603 Type
Paleobiology Depart. NMNH, Smithsonian Institution
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
HOLOTYPE INFO:
Holotype: USNM 466603 (Originally UT 996) (Adkins, 1930).
Locality: Fort Worth, Tarrant County, Texas (Adkins, 1930).
Stratigraphy: Weno Formation, 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 obesus Adkins, 1930
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
A very large Macraster distinguished by its "obese," highly inflated profile and high vertical sides. The test is cordate with a distinct anterior notch. Ambulacra are long, deeply sunken, and extend almost to the ambitus. Distinguished from M. elegans by its greater height relative to length and width (Adkins, 1930).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Weno Formation (Adkins, 1930); Fort Worth Limestone.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Grayson, Tarrant.
Abundance: Rare; typically found in the upper Washita Group.
DESCRIPTION
TOP: Length, width, height: 98.4 mm L × 93.0 mm W × 57.1 mm H.
Top shape: Cordate with a very angular margin. Pointed posteriorly.
Top domed: Very inflated; apex is located slightly posterior of the midpoint. Adkins (1930) notes the highest point is posterior to the apical system.
SIDE: Ambitus: Positioned approximately 38% from the base.
Side shape: Very inflated; "obese."
Profile: Anterior end is long and truncated; posterior end is sloping. From the ends, the test appears broad and very rounded.
BOTTOM: Bottom shape: Mostly flat, yet slightly curved/convex.
AMB: Amb shape: All 5 ambulacra are equally sunken.
Amb arrangement: Paired ambulacra are wide, lanceolate, slightly flexuous, and open at the outer ends. Anterior paired ambulacra are slightly longer than the posterior pair and almost reach the margin (Adkins, 1930).
Unpaired Amb: Narrower than the paired ambulacra.
PORE PAIRS: Arrangement: Unpaired ambulacrum pores are slightly elongated and arranged en chevron.
Shape: Pores in paired ambulacra are elongated.
TUBERCLES: Primary Perforated: Yes.
Primary Crenulate: Yes.
Distribution: Tubercles and granulation are mostly even over the entire test.
Areolas: Sunken.
INTERAMB: Shape: All 5 interambulacra are raised. The posterior interambulacrum features a large flattened surface.
GRANULES: Distribution: Evenly distributed.
FASCIOLE: Absent in Macraster).
APICAL SYSTEM: Size: Small.
Plating: Madreporite constitutes about 1/4 of the apical system.
Genital Pores: 4 gonopores (Adkins, 1930).
PERIPROCT (ANUS): Shape: Small; longitudinally oval with both ends pointed.
Location: Situated slightly above the midpoint.
Visibility: Barely visible from above.
PERISTOME (MOUTH): Shape: Subpentagonal; wide.
Size: Depressed; about equal in size to the periproct.
Location: Located about 25% from the anterior margin.
Visibility: Cannot be seen from the anterior end.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype USNM 466603 (Specimen in photos).
ETYMOLOGY
From the Latin obesus (fat, stout, plump), referring to the highly inflated profile of the test (Adkins, 1930).
REMARKS & COMPARISONS
Remarks: Adkins (1930) described M. obesus as having a "very tall, inflated test" differing from M. elegans by its proportions. However, Kamyabi Shadan et al. (2014) regard M. obesus as a synonym of Macraster elegans (Shumard, 1853), stating that the high number of species names for large, inflated Macraster in North America is an overestimation based on local ecophenotypic variants.
Comparisons:
- M. elegans: M. obesus is historically distinguished by being taller and more "obese," with a higher ambitus and straighter sides than the typical M. elegans.
