Mecaster batnensis (Maury, 1923)
Plate: MeBa-10
Series: Upper Cretaceous Group: Eagle Ford Formation: Eagle Ford
Locale: Austin County: Travis Stage: Turonian
Length: 32.9 mm Width: 29.5 mm Height: 22.1 mm
Specimen in photo: NPL 83026 Hypotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: Originally described by Coquand (1862). Repository likely MNHN (Paris).
Locality: Batna, Algeria.
Stratigraphy: Turonian.
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: Hemiasteridae H. L. Clark, 1917
Genus: MECASTER Pomel, 1883
Species: Mecaster batnensis (Coquand, 1862)
TYPE SPECIES: Hemiaster fourneli Agassiz & Desor, 1847
DIAGNOSIS
Test suboval and inflated with a steep posterior truncation. Petals are straight, sunken, and V-shaped; the anterior pair is longer. Characterized by an ethmophract apical system and a broad, indented peripetalous fasciole.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Eagle Ford
Formations: Eagle Ford Formation; Boquillas Formation.
Stratigraphic Units: Upper Cretaceous, Turonian.
Counties: Travis, Dallas (Type of H. jacksoni).
Abundance: Common in the Eagle Ford Shale.
DESCRIPTION
TOP: Length, width, height: 32.9 mm L × 29.5 mm W × 22.1 mm H.
Top shape: Suboval; heart-shaped (Cooke, 1953). Emarginate in front; widest in front of the center.
Top domed: Upper surface inflated (Cooke, 1953).
SIDE: Ambitus: Rounded margin.
Side shape: Posterior truncation is steep (Cooke, 1953).
BOTTOM: Bottom shape: Lower surface flattish; slightly convex in the sternal region (Cooke, 1953).
AMB: Amb shape: Anterior ambulacrum (III) is depressed in a broad depression which extends to the peristome, slightly indenting the margin.
Amb arrangement: Paired petals are V-shaped, straight, and sunken. They are rather long, with the anterior pair being longer than the posterior pair (Cooke, 1953).
PORE PAIRS: Shape: Pores in paired petals are elongated and not conjugate (Cooke, 1953). Pores in the anterior ambulacrum are small, close together, and arranged in diagonal pairs; inclination increases away from the apex.
Arrangement: Poriferous zones are somewhat wider than the interporiferous zones (Cooke, 1953).
TUBERCLES: Distribution: Rather widely scattered; larger on the anterior end (Cooke, 1953).
GRANULES: Not specified.
FASCIOLE: Peripetalous: Broad and rather ill-defined; strongly indented on each side between the petals (Cooke, 1953).
APICAL SYSTEM: Location: Central (Cooke, 1953).
Genital pores: Four genital pores; lateral perforations closer together than front or back pairs.
Type: Ethmophract; the madreporite extends between the posterior lateral genital plates but does not separate the posterior ocular plates, which are in contact (Cooke, 1953).
PERIPROCT (ANUS): Location: Located high up on the posterior truncation.
Visibility: Plainly visible from above (Cooke, 1953).
PERISTOME (MOUTH): Shape: Reniform (kidney-shaped) or subpentagonal.
Location: At the anterior third.
Lip: Weak posterior lip (Cooke, 1953).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83026. Collected by William R. Thompson, Jr.
ETYMOLOGY
Named for the city of Batna, Algeria, the type locality of Hemiaster batnensis.
REMARKS & COMPARISONS
Remarks: This species is well known in the American literature as Hemiaster jacksoni Clark, 1915. However, it is morphologically consistent with Mecaster batnensis described from the Turonian of North Africa and Europe. The presence of an ethmophract apical system (posterior oculars in contact) is described by Cooke (1953), which is a character often associated with Hemiaster sensu stricto, though the species is widely accepted as Mecaster in modern Cretaceous taxonomy due to petal and fasciole structure.
Plate: MeBa-10
Series: Upper Cretaceous Group: Eagle Ford Formation: Eagle Ford
Locale: Austin County: Travis Stage: Turonian
Length: 32.9 mm Width: 29.5 mm Height: 22.1 mm
Specimen in photo: NPL 83026 Hypotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: Originally described by Coquand (1862). Repository likely MNHN (Paris).
Locality: Batna, Algeria.
Stratigraphy: Turonian.
SYNONYMY
- Hemiaster batnensis Maury, 1923 — original description (Batna, Algeria; Turonian)
- Hemiaster jacksoni Clark, 1915 — junior synonym (Texas; Eagle Ford Group)
- Mecaster jacksoni (Clark, 1915) Cooke, 1953 — recombination
- Mecaster batnensis (Maury, 1923) Smith & Bengtson, 1991 — synonymy established
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: Hemiasteridae H. L. Clark, 1917
Genus: MECASTER Pomel, 1883
Species: Mecaster batnensis (Coquand, 1862)
TYPE SPECIES: Hemiaster fourneli Agassiz & Desor, 1847
DIAGNOSIS
Test suboval and inflated with a steep posterior truncation. Petals are straight, sunken, and V-shaped; the anterior pair is longer. Characterized by an ethmophract apical system and a broad, indented peripetalous fasciole.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Eagle Ford
Formations: Eagle Ford Formation; Boquillas Formation.
Stratigraphic Units: Upper Cretaceous, Turonian.
Counties: Travis, Dallas (Type of H. jacksoni).
Abundance: Common in the Eagle Ford Shale.
DESCRIPTION
TOP: Length, width, height: 32.9 mm L × 29.5 mm W × 22.1 mm H.
Top shape: Suboval; heart-shaped (Cooke, 1953). Emarginate in front; widest in front of the center.
Top domed: Upper surface inflated (Cooke, 1953).
SIDE: Ambitus: Rounded margin.
Side shape: Posterior truncation is steep (Cooke, 1953).
BOTTOM: Bottom shape: Lower surface flattish; slightly convex in the sternal region (Cooke, 1953).
AMB: Amb shape: Anterior ambulacrum (III) is depressed in a broad depression which extends to the peristome, slightly indenting the margin.
Amb arrangement: Paired petals are V-shaped, straight, and sunken. They are rather long, with the anterior pair being longer than the posterior pair (Cooke, 1953).
PORE PAIRS: Shape: Pores in paired petals are elongated and not conjugate (Cooke, 1953). Pores in the anterior ambulacrum are small, close together, and arranged in diagonal pairs; inclination increases away from the apex.
Arrangement: Poriferous zones are somewhat wider than the interporiferous zones (Cooke, 1953).
TUBERCLES: Distribution: Rather widely scattered; larger on the anterior end (Cooke, 1953).
GRANULES: Not specified.
FASCIOLE: Peripetalous: Broad and rather ill-defined; strongly indented on each side between the petals (Cooke, 1953).
APICAL SYSTEM: Location: Central (Cooke, 1953).
Genital pores: Four genital pores; lateral perforations closer together than front or back pairs.
Type: Ethmophract; the madreporite extends between the posterior lateral genital plates but does not separate the posterior ocular plates, which are in contact (Cooke, 1953).
PERIPROCT (ANUS): Location: Located high up on the posterior truncation.
Visibility: Plainly visible from above (Cooke, 1953).
PERISTOME (MOUTH): Shape: Reniform (kidney-shaped) or subpentagonal.
Location: At the anterior third.
Lip: Weak posterior lip (Cooke, 1953).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83026. Collected by William R. Thompson, Jr.
ETYMOLOGY
Named for the city of Batna, Algeria, the type locality of Hemiaster batnensis.
REMARKS & COMPARISONS
Remarks: This species is well known in the American literature as Hemiaster jacksoni Clark, 1915. However, it is morphologically consistent with Mecaster batnensis described from the Turonian of North Africa and Europe. The presence of an ethmophract apical system (posterior oculars in contact) is described by Cooke (1953), which is a character often associated with Hemiaster sensu stricto, though the species is widely accepted as Mecaster in modern Cretaceous taxonomy due to petal and fasciole structure.
