Tetragramma cranei Thompson, 2016
Plate: TeCr-10
Series: Lower Cretaceous Group: Washita Formation: Duck Creek
Locale: Fort Worth County: Tarrant Stage: Albian
Length: 27.7 mm Height: 7.3 mm
Specimen in photo: NPL 82988 Holotype
Collector: Stephen Crane
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 82988 .
Locality: General Portland Cement Quarry, Fort Worth, Tarrant County, Texas.
Stratigraphy: Duck Creek Formation, Washita 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: Diplopodiidae Smith & Wright, 1993
Genus: TETRAGRAMMA L. Agassiz, 1838
Species: Tetragramma cranei Thompson, 2016
TYPE SPECIES: Cidarites variolare Brongniart, 1822
DIAGNOSIS
A small Tetragramma with a very flattened test and a round to slightly pentagonal outline. Interambulacra bear six rows of perforated, crenulate primary tubercles at the ambitus, arranged as two full‑length rows, two mid‑length rows, and two short rows restricted to the region just above and below the ambitus. Ambulacra are narrow and lanceolate, with two rows of 8 primary tubercles, largest at the ambitus. Ambulacral plating is quinqueminate (5 elements) aborally and trigeminate (3 elements) adorally. Pore pairs are uniserial below the ambitus and biserial above. Granulation sparse aborally and thinning adorally near the peristome. Apical system moderately large (36% of test diameter), subpentagonal, cutting deeply into each interambulacrum. Peristome circular (34% of test diameter) with pronounced buccal notches.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Duck Creek Formation.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Tarrant.
Abundance: Rare; only one specimen found.
DESCRIPTION
TOP: Length, width, height: 27.7 mm L × 7.3 mm H. Top shape: Round; margin rounded. Top domed: Very flattened upper and lower surface. Concave around apical system.
SIDE: Ambitus: Positioned at midpoint. Side shape: Flattened, with minimal inflation.
BOTTOM: Bottom shape: Very flattened; with a shallow concavity around the peristome.
AMB: Amb shape: Lanceolate; widest at ambitus, narrows at apical system and peristome. Amb arrangement: Two rows of 8 tubercles. Width: Interambulacra are twice the size of ambulacra at the margin. Plating: Quinqueminate (5 elements) aborally; trigeminate (3 elements) adorally.
PORE PAIRS: Arrangement: Uniserial below margin; biserial above margin.
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: Yes. Bosses: Small. Ambulacral Tubercles: Largest at ambitus, decreasing in size moving away. Interambulacral Tubercles: 6 rows at the margin. Two rows of 12 run the entire length (widening near apical system); two rows of 9 run from below half-way above margin to 2/3 below; two rows of 5 run from just above margin to just under half below. Center rows do not decrease much in size until close to apical system. Scrobicular Tubercles: Present above and below the margin, then grow faint.
GRANULES: Distribution: Np perradoa; granulation aborally. Adoral perradial granulation thins near the peristome.
APICAL SYSTEM: Size: Diameter 36% of test. Shape: Subpentagonal; cuts deep into each interambulacrum and slightly into each ambulacrum.
PERIPROCT (ANUS): (Unknown).
PERISTOME (MOUTH): Size: Diameter 34% of test. Shape: Circular. Lip: Buccal notches pronounced.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen: Holotype NPL 82988. Found by Stephen Crane.
ETYMOLOGY
Named after Dr. Stephen Crane (1946-2020) who found the specimen.
REMARKS & COMPARISONS
Remarks: Tetragramma cranei shares the feature of having six rows of tubercles at the margin with Tetragramma donaldtrumpi and with Tetragramma adami (now Strictotiara adami). However, T. cranei differs by having smaller bosses, fewer ambulacral tubercles, and a pentagonal apical system. The species also lacks aboral perradial granules.
Comparisons:
Plate: TeCr-10
Series: Lower Cretaceous Group: Washita Formation: Duck Creek
Locale: Fort Worth County: Tarrant Stage: Albian
Length: 27.7 mm Height: 7.3 mm
Specimen in photo: NPL 82988 Holotype
Collector: Stephen Crane
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 82988 .
Locality: General Portland Cement Quarry, Fort Worth, Tarrant County, Texas.
Stratigraphy: Duck Creek Formation, Washita 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: Diplopodiidae Smith & Wright, 1993
Genus: TETRAGRAMMA L. Agassiz, 1838
Species: Tetragramma cranei Thompson, 2016
TYPE SPECIES: Cidarites variolare Brongniart, 1822
DIAGNOSIS
A small Tetragramma with a very flattened test and a round to slightly pentagonal outline. Interambulacra bear six rows of perforated, crenulate primary tubercles at the ambitus, arranged as two full‑length rows, two mid‑length rows, and two short rows restricted to the region just above and below the ambitus. Ambulacra are narrow and lanceolate, with two rows of 8 primary tubercles, largest at the ambitus. Ambulacral plating is quinqueminate (5 elements) aborally and trigeminate (3 elements) adorally. Pore pairs are uniserial below the ambitus and biserial above. Granulation sparse aborally and thinning adorally near the peristome. Apical system moderately large (36% of test diameter), subpentagonal, cutting deeply into each interambulacrum. Peristome circular (34% of test diameter) with pronounced buccal notches.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Duck Creek Formation.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Tarrant.
Abundance: Rare; only one specimen found.
DESCRIPTION
TOP: Length, width, height: 27.7 mm L × 7.3 mm H. Top shape: Round; margin rounded. Top domed: Very flattened upper and lower surface. Concave around apical system.
SIDE: Ambitus: Positioned at midpoint. Side shape: Flattened, with minimal inflation.
BOTTOM: Bottom shape: Very flattened; with a shallow concavity around the peristome.
AMB: Amb shape: Lanceolate; widest at ambitus, narrows at apical system and peristome. Amb arrangement: Two rows of 8 tubercles. Width: Interambulacra are twice the size of ambulacra at the margin. Plating: Quinqueminate (5 elements) aborally; trigeminate (3 elements) adorally.
PORE PAIRS: Arrangement: Uniserial below margin; biserial above margin.
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: Yes. Bosses: Small. Ambulacral Tubercles: Largest at ambitus, decreasing in size moving away. Interambulacral Tubercles: 6 rows at the margin. Two rows of 12 run the entire length (widening near apical system); two rows of 9 run from below half-way above margin to 2/3 below; two rows of 5 run from just above margin to just under half below. Center rows do not decrease much in size until close to apical system. Scrobicular Tubercles: Present above and below the margin, then grow faint.
GRANULES: Distribution: Np perradoa; granulation aborally. Adoral perradial granulation thins near the peristome.
APICAL SYSTEM: Size: Diameter 36% of test. Shape: Subpentagonal; cuts deep into each interambulacrum and slightly into each ambulacrum.
PERIPROCT (ANUS): (Unknown).
PERISTOME (MOUTH): Size: Diameter 34% of test. Shape: Circular. Lip: Buccal notches pronounced.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen: Holotype NPL 82988. Found by Stephen Crane.
ETYMOLOGY
Named after Dr. Stephen Crane (1946-2020) who found the specimen.
REMARKS & COMPARISONS
Remarks: Tetragramma cranei shares the feature of having six rows of tubercles at the margin with Tetragramma donaldtrumpi and with Tetragramma adami (now Strictotiara adami). However, T. cranei differs by having smaller bosses, fewer ambulacral tubercles, and a pentagonal apical system. The species also lacks aboral perradial granules.
Comparisons:
- Strictotiara adami: T. cranei differs by having larger bosses, more tubercles in the ambulacra, and an apical scar with a pentagonal shape. T. cranei is also has no aboral granules in perradial.
- Tetragramma donaldtrumpi: T. cranei differs by having larger bosses, more tubercles in the ambulacra, trigeminate plating adorally, and a pentagonal shape.
