Macraster wenoensis (Adkins, 1920)
Plate: MaWe-10
Series: Lower Cretaceous Group: Washita Formation: Weno
Locale: Fort Worth County: Tarrant Stage: Albian
Length: 56.7 mm Width: 51.1 mm Height: 31.7 mm
Specimen in photos: BEG 21467 Holotype
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: BEG 21467 (Adkins, 1920).
Locality: Fort Worth, Tarrant County, Texas.
Stratigraphy: Weno Formation (Basal third, marl facies).
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 wenoensis (Adkins, 1920)
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
Test inflated, rotund, and smooth; smaller and less inflated than M. elegans. Ambulacra are narrow, nearly straight, and only slightly depressed. Distinguished by conspicuous "crater-like" peristomal pore knobs and a trapezoidal periproct (Adkins, 1920).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Weno Formation (basal third); Pawpaw Formation (marl facies) (Adkins, 1920).
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Tarrant.
Abundance: Abundant in the basal Weno marls of North Texas.
Associated Fauna: Holaster sp. aff. simplex, Enallaster bravoensis, Hemiaster calvini (Adkins, 1920).
DESCRIPTION
TOP: Length, width, height: 56.7 mm L × 51.1 mm W × 31.7 mm H.
Top shape: Rotund; widest point just anterior of the apical system. Posterior end narrowed to a point.
Top domed: Smooth and inflated. Tallest point is on the mid-line posterior to the apical system (one-third the distance to the ambitus).
SIDE: Ambitus: Rounded; greatest perimeter at the bottom. Anterolateral angulation present just back of where the ambulacra cross the ambitus.
Side shape: Inflated; rather straight-sided. Posterior end is very narrowly truncated.
BOTTOM: Bottom shape: Adoral side nearly flat; excavated for the peristome. Slightly raised on the posterior mid-line.
AMB: Amb shape: Nearly straight and only slightly depressed.
Amb arrangement: Anterolaterals (II & IV) diverge at ~150°, then turn forward slightly. Posterolaterals (I & V) are long, straight, and diverge at ~60°.
Unpaired Amb: Amb III lies in a shallow anterior sulcus; similar in form to paired grooves but slightly narrower. Contains ~31 pore pairs set at a slight angle.
PORE PAIRS: Shape: Short and slit-like.
Arrangement: Anterolaterals have ~50 pore pairs; Posterolaterals have ~54 pore pairs. Pores in the anterolaterals are not set at an angle to each other.
Peristomal Pores: Distinctive feature: Upon approaching the peristome, pores are borne on elevated knobs with crater-like openings. Anterolateral rows have 8–9 cup-like elevations; posterolateral rows have ~5 smaller craters (Adkins, 1920).
TUBERCLES: Distribution: Smooth in appearance; sparsely tuberculated aborally (Adkins, 1920).
GRANULES: Distribution: Ambulacra crossing the ambitus continue as smooth, finely granulated strips.
FASCIOLE: Absent. Adkins notes that Texas "Epiaster" material (now Macraster) entirely lacks fascioles.
APICAL SYSTEM: Location: Anterior of center (proportionately farther forward than in M. subobesus).
PERIPROCT (ANUS): Shape: Trapezoidal with rounded angles; broader at the bottom than at the top.
Location: Situated on the narrow posterior truncation.
PERISTOME (MOUTH): Shape: Oval; long axis transverse.
Lip: Posterior margin has a central, bluntly rounded, forward-projecting keel/lip (Adkins, 1920).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype BEG 21467 studied by Adkins.
ETYMOLOGY
Named for the Weno Formation, the stratigraphic unit where the species is most abundant.
REMARKS & COMPARISONS
Remarks: Originally described as Epiaster wenoensis. Adkins (1920) noted the taxonomic confusion between Hemiaster, Epiaster, and Macraster in the Texas Cretaceous, largely hinging on the preservation of fascioles. Modern classification places these large, non-fasciolate forms in Macraster. Kamyabi Shadan et al. (2014) suggest this may be a synonym of Macraster elegans, but Adkins specifically distinguished it based on the straightness of the ambulacra and the "crater-like" oral pores.
Comparisons:
Plate: MaWe-10
Series: Lower Cretaceous Group: Washita Formation: Weno
Locale: Fort Worth County: Tarrant Stage: Albian
Length: 56.7 mm Width: 51.1 mm Height: 31.7 mm
Specimen in photos: BEG 21467 Holotype
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: BEG 21467 (Adkins, 1920).
Locality: Fort Worth, Tarrant County, Texas.
Stratigraphy: Weno Formation (Basal third, marl facies).
SYNONYMY
- Epiaster wenoensis Adkins, 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 wenoensis (Adkins, 1920)
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
Test inflated, rotund, and smooth; smaller and less inflated than M. elegans. Ambulacra are narrow, nearly straight, and only slightly depressed. Distinguished by conspicuous "crater-like" peristomal pore knobs and a trapezoidal periproct (Adkins, 1920).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Weno Formation (basal third); Pawpaw Formation (marl facies) (Adkins, 1920).
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Tarrant.
Abundance: Abundant in the basal Weno marls of North Texas.
Associated Fauna: Holaster sp. aff. simplex, Enallaster bravoensis, Hemiaster calvini (Adkins, 1920).
DESCRIPTION
TOP: Length, width, height: 56.7 mm L × 51.1 mm W × 31.7 mm H.
Top shape: Rotund; widest point just anterior of the apical system. Posterior end narrowed to a point.
Top domed: Smooth and inflated. Tallest point is on the mid-line posterior to the apical system (one-third the distance to the ambitus).
SIDE: Ambitus: Rounded; greatest perimeter at the bottom. Anterolateral angulation present just back of where the ambulacra cross the ambitus.
Side shape: Inflated; rather straight-sided. Posterior end is very narrowly truncated.
BOTTOM: Bottom shape: Adoral side nearly flat; excavated for the peristome. Slightly raised on the posterior mid-line.
AMB: Amb shape: Nearly straight and only slightly depressed.
Amb arrangement: Anterolaterals (II & IV) diverge at ~150°, then turn forward slightly. Posterolaterals (I & V) are long, straight, and diverge at ~60°.
Unpaired Amb: Amb III lies in a shallow anterior sulcus; similar in form to paired grooves but slightly narrower. Contains ~31 pore pairs set at a slight angle.
PORE PAIRS: Shape: Short and slit-like.
Arrangement: Anterolaterals have ~50 pore pairs; Posterolaterals have ~54 pore pairs. Pores in the anterolaterals are not set at an angle to each other.
Peristomal Pores: Distinctive feature: Upon approaching the peristome, pores are borne on elevated knobs with crater-like openings. Anterolateral rows have 8–9 cup-like elevations; posterolateral rows have ~5 smaller craters (Adkins, 1920).
TUBERCLES: Distribution: Smooth in appearance; sparsely tuberculated aborally (Adkins, 1920).
GRANULES: Distribution: Ambulacra crossing the ambitus continue as smooth, finely granulated strips.
FASCIOLE: Absent. Adkins notes that Texas "Epiaster" material (now Macraster) entirely lacks fascioles.
APICAL SYSTEM: Location: Anterior of center (proportionately farther forward than in M. subobesus).
PERIPROCT (ANUS): Shape: Trapezoidal with rounded angles; broader at the bottom than at the top.
Location: Situated on the narrow posterior truncation.
PERISTOME (MOUTH): Shape: Oval; long axis transverse.
Lip: Posterior margin has a central, bluntly rounded, forward-projecting keel/lip (Adkins, 1920).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype BEG 21467 studied by Adkins.
ETYMOLOGY
Named for the Weno Formation, the stratigraphic unit where the species is most abundant.
REMARKS & COMPARISONS
Remarks: Originally described as Epiaster wenoensis. Adkins (1920) noted the taxonomic confusion between Hemiaster, Epiaster, and Macraster in the Texas Cretaceous, largely hinging on the preservation of fascioles. Modern classification places these large, non-fasciolate forms in Macraster. Kamyabi Shadan et al. (2014) suggest this may be a synonym of Macraster elegans, but Adkins specifically distinguished it based on the straightness of the ambulacra and the "crater-like" oral pores.
Comparisons:
- M. elegans: M. wenoensis is smaller, smoother, less inflated, and has straighter/narrower ambulacra than M. elegans.
- M. aguilerae: M. wenoensis is smaller, more pointed posteriorly, and has a shallower anterior sulcus notch.
