Miocyphosoma occultatum Thompson, 2020
Plate: MiOc-10
Series: Lower Cretaceous Group: Fredericksburg Formation: Comanche Peak
Locale: Harker Heights County: Bell Stage: Albian
Width: 19.0 mm Height: 7.7 mm
Collector: William Thompson
Specimen in Photo: NPL 94348
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 94348 .
Paratype: NPL 94349 .
Locality: Harker Heights, Bell County, Texas.
Stratigraphy: Comanche Peak Formation, Fredericksburg Group.
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Carinacea Kroh & Smith, 2010
Superorder: Calycina Gregory, 1900
Order: Phymosomatoida Mortensen, 1904
Family: Phymosomatidae Pomel, 1883
Genus: MIOCYPHOSOMA Pomel, 1883
Species: Miocyphosoma occultatum Thompson, 2020
TYPE SPECIES: Cidaris wetherelli Forbes, 1850
DIAGNOSIS
A small Miocyphosoma from the Albian of Texas characterized by distinctly crenulate tubercles and pore pairs that are uniserial from the adapical surface to the apex. Distinguished by adradial and interradial bands of granules.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Fredericksburg
Formations: Comanche Peak Formation.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Bell (Holotype), Johnson (Paratype).
Abundance: Rare; two specimens known.
DESCRIPTION
TOP: Length, width, height: 19.0 mm L × 7.7 mm H.
Top shape: Round outline.
Top domed: Apical system is angular and measures 1/3 of the test diameter.
SIDE: Ambitus: Rounded; positioned at 40% of height from the adoral surface.
Side shape: Inflated.
BOTTOM: Bottom shape: Adoral surface very slightly concave.
AMB: Amb shape: Lanceolate; width at the apical system is almost twice the width at the peristome.
Amb arrangement: Ambulacra are 44% the width of the interambulacra at the ambitus. Two rows of large tubercles (7 to 8 in each) gradually diminish in size toward the poles.
Plating: Phymosomatid plate compounding; 5 elements (quinqueminate).
PORE PAIRS: Arrangement: Undulated, especially on the aboral surface. Uniserial adapically to the apex.
Irregularity: In one ambulacrum on the adoral surface, 6 sets of pore pairs shift to an almost biserial arrangement before becoming uniserial again.
TUBERCLES: Primary Perforated: No (Imperforate).
Primary Crenulate: Yes (Distinctly crenulate).
Interambulacral Tubercles: Two perpendicular rows of large tubercles (7 to 8 in each), only slightly larger than the ambulacral tubercles. Size diminishes gradually toward the poles, but less so than in the ambulacra.
Areolas: Large; dominate the plates.
GRANULES: Distribution: Rows of granules present at adradial and interradial margins. Ambulacral granulation is sparse compared to congeners.
FASCIOLE: Absent.
APICAL SYSTEM: Size: Diameter 1/3 of test.
Shape: Angular, pentagonal.
Condition: Plating lost.
PERIPROCT (ANUS): (Unknown).
PERISTOME (MOUTH): Size: Large; diameter 50% (1/2) of test.
Shape: Round.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Two specimens studied. Holotype NPL 94348 (Bell County) and Paratype NPL 94349 (Johnson County).
ETYMOLOGY
From the Latin occultatum ("hidden"), referring to the fact that the holotype was hidden among numerous Phymosoma and Tetragramma specimens.
REMARKS & COMPARISONS
Remarks: This species is assigned to Miocyphosoma based on the 5-element ambulacral plating and general architecture.
Comparisons:
Plate: MiOc-10
Series: Lower Cretaceous Group: Fredericksburg Formation: Comanche Peak
Locale: Harker Heights County: Bell Stage: Albian
Width: 19.0 mm Height: 7.7 mm
Collector: William Thompson
Specimen in Photo: NPL 94348
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 94348 .
Paratype: NPL 94349 .
Locality: Harker Heights, Bell County, Texas.
Stratigraphy: Comanche Peak Formation, Fredericksburg Group.
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Carinacea Kroh & Smith, 2010
Superorder: Calycina Gregory, 1900
Order: Phymosomatoida Mortensen, 1904
Family: Phymosomatidae Pomel, 1883
Genus: MIOCYPHOSOMA Pomel, 1883
Species: Miocyphosoma occultatum Thompson, 2020
TYPE SPECIES: Cidaris wetherelli Forbes, 1850
DIAGNOSIS
A small Miocyphosoma from the Albian of Texas characterized by distinctly crenulate tubercles and pore pairs that are uniserial from the adapical surface to the apex. Distinguished by adradial and interradial bands of granules.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Fredericksburg
Formations: Comanche Peak Formation.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Bell (Holotype), Johnson (Paratype).
Abundance: Rare; two specimens known.
DESCRIPTION
TOP: Length, width, height: 19.0 mm L × 7.7 mm H.
Top shape: Round outline.
Top domed: Apical system is angular and measures 1/3 of the test diameter.
SIDE: Ambitus: Rounded; positioned at 40% of height from the adoral surface.
Side shape: Inflated.
BOTTOM: Bottom shape: Adoral surface very slightly concave.
AMB: Amb shape: Lanceolate; width at the apical system is almost twice the width at the peristome.
Amb arrangement: Ambulacra are 44% the width of the interambulacra at the ambitus. Two rows of large tubercles (7 to 8 in each) gradually diminish in size toward the poles.
Plating: Phymosomatid plate compounding; 5 elements (quinqueminate).
PORE PAIRS: Arrangement: Undulated, especially on the aboral surface. Uniserial adapically to the apex.
Irregularity: In one ambulacrum on the adoral surface, 6 sets of pore pairs shift to an almost biserial arrangement before becoming uniserial again.
TUBERCLES: Primary Perforated: No (Imperforate).
Primary Crenulate: Yes (Distinctly crenulate).
Interambulacral Tubercles: Two perpendicular rows of large tubercles (7 to 8 in each), only slightly larger than the ambulacral tubercles. Size diminishes gradually toward the poles, but less so than in the ambulacra.
Areolas: Large; dominate the plates.
GRANULES: Distribution: Rows of granules present at adradial and interradial margins. Ambulacral granulation is sparse compared to congeners.
FASCIOLE: Absent.
APICAL SYSTEM: Size: Diameter 1/3 of test.
Shape: Angular, pentagonal.
Condition: Plating lost.
PERIPROCT (ANUS): (Unknown).
PERISTOME (MOUTH): Size: Large; diameter 50% (1/2) of test.
Shape: Round.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Two specimens studied. Holotype NPL 94348 (Bell County) and Paratype NPL 94349 (Johnson County).
ETYMOLOGY
From the Latin occultatum ("hidden"), referring to the fact that the holotype was hidden among numerous Phymosoma and Tetragramma specimens.
REMARKS & COMPARISONS
Remarks: This species is assigned to Miocyphosoma based on the 5-element ambulacral plating and general architecture.
Comparisons:
- Miocyphosoma bexarense: M. occultatum has distinctly crenulated tubercles, whereas M. bexarense is only slightly crenulate. The granulation in the ambulacra of M. occultatum is much less dense than in M. bexarense. The peristome of M. occultatum is less pentagonal (rounder).
- Gauthieria paucituberculata: The peristome of M. occultatum is much larger than that of G. paucituberculata.
