Tetragramma streeruwitzi (Cragin, 1893)
Plate: TeSt-10
Series: Upper Cretaceous Group: Washita Formation: Boracho
Locale: Rio Grande County: El Paso Stage: Cenomanian
Length: 36.0 mm Height: 11.8 mm
Specimen in photos: U.S.N.M. 474149
Paleobiology Depart. NMNH, Smithsonian Institution
Collector: (Not specified)
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
HOLOTYPE INFO:
Syntypes: Originally described by Cragin (1893). Repository likely USNM or UT (BEG). Exact syntype repository uncertain; Cragin did not designate a holotype.
Locality: Sierra Blanca Mountains, El Paso (now Hudspeth) County, Texas.
Stratigraphy: Washita Group (Comanche Series).
SYNONYMY
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 streeruwitzi (Cragin, 1893)
TYPE SPECIES: Cidarites variolare Brongniart, 1822
DIAGNOSIS
A Tetragramma characterized by a subcircular, very depressed test (flattened above and below). Interambulacra feature a high number of tubercle rows at the ambitus (8 to 10), which reduce significantly aborally. The apical scar is narrow and elongate (Cragin, 1893).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Boracho Formation.
Stratigraphic Units: Upper Cretaceous, Cenomanian.
Counties: Hudspeth (Sierra Blanca), El Paso, Culberson (Kent).
Abundance: Uncommon; confined to West Texas.
DESCRIPTION
TOP: Length, width, height: 36.0 mm L × 11.8 mm H. Top shape: Subcircular to very slightly quinquelateral. Top domed: Decidedly depressed; flattened almost as much above as below (Cragin, 1893). Cragin's syntype was larger (Breadth 44 mm).
SIDE: Ambitus: Ambitus at midpoint. Side shape: Depressed profile.
BOTTOM: Bottom shape: Distinctly flattened; considerably inverted around the peristome.
AMB: Amb shape: Moderate width; straight. Amb arrangement: Two vertical rows of primary tubercles, comparable in size to the central interambulacral rows at the ambitus. Width: Interambulacra are nearly 3 times the width of the ambulacra.
PORE PAIRS: Arrangement: Simple (uniserial) at the ambitus; biserial aborally (toward apical system) and crowded near the peristome. Poriferous zones are wide above the ambitus but narrow at the ambitus (Clark & Twitchell, 1915).
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: Yes. Interambulacral Tubercles: High density at ambitus (6 to 8 rows per Clark; up to 10 rows per Cragin in syntype material). The constituent tubercles decrease in size from the center of the plate outward. Rows gradually disappear aborally.
GRANULES: Distribution: Miliary zone on lower half contains two alternatin rows of small secondary tubercles.
APICAL SYSTEM: Size: Medium. Shape: Apical scar (cicatrix) is narrow and elongate. Features: The posterior angle of the cicatrix forms a capacious, rounded emargination that invades the interambulacral area deeply. (Cragin, 1893).
PERIPROCT (ANUS): (Unknown).
PERISTOME (MOUTH): Size: Small. Lip: Not very large. Buccal margin simple.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype USNM 474149.
ETYMOLOGY
Named in honor of W. H. von Streeruwitz (1833–1916), geologist with the Geological Survey of Texas who collected the type material.
REMARKS & COMPARISONS
Remarks: Cragin (1893) placed this in Diplopodia (a synonym of Tetragramma) and noted its affinity to T. malbosii (of Europe) and T. taffi.
Tetragramma streeruwitzi is one of the most distinctive Texas Tetragramma due to its very depressed test, high number of interambulacral tubercle rows, and narrow, elongate apical scar. The species shows 8–10 rows at the ambitus (depending on author), far exceeding the row counts of Glen Rose and Washita species to the east. The test is flattened above and below to a degree not seen in other Texas forms, and the apical scar is proportionally narrower and more elongate than in any other regional species. The species is confined to far West Texas, occurring only in the Boracho Formation and equivalent Washita units of the Sierra Blanca region. Cragin’s original material was larger than the hypotype figured here, but the depressed profile, high tubercle density, and elongate cicatrix are consistent across all known specimens.
Comparisons:
• Tetragramma malbosii (Europe): T. streeruwitzi is more depressed, with a smaller, narrower, and more elongate apical scar. It also has more interambulacral tubercle rows on the lower half of the test than similarly sized T. malbosii. The European species is more inflated and has a broader cicatrix.
• Tetragramma taffi (Texas): T. taffi is much larger and more inflated, with 8–10 rows but arranged differently and lacking the extreme flattening of T. streeruwitzi. The apical system of T. taffi is broader and not as elongate.
• Tetragramma goodlandense (Texas): T. goodlandense has six rows plus secondary rows, but the test is not nearly as depressed, and the apical scar is wider and more pentagonal. T. streeruwitzi is flatter and has more rows at the ambitus.
• Tetragramma hammerschmidti (Texas): T. hammerschmidti has six rows with high tubercle counts but is moderately inflated, not depressed. Its apical system is round, not elongate.
• Tetragramma glenrosense (Texas): T. glenrosense has only four rows and a more inflated test. The apical system is pentagonal and broader. T. streeruwitzi is far more depressed and has many more rows.
• Tetragramma cranei (Texas): T. cranei is much smaller, with six rows arranged in a 12–9–5 pattern, and has a pentagonal apical system. It lacks the extreme flattening and high row counts of T. streeruwitzi.
Plate: TeSt-10
Series: Upper Cretaceous Group: Washita Formation: Boracho
Locale: Rio Grande County: El Paso Stage: Cenomanian
Length: 36.0 mm Height: 11.8 mm
Specimen in photos: U.S.N.M. 474149
Paleobiology Depart. NMNH, Smithsonian Institution
Collector: (Not specified)
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
HOLOTYPE INFO:
Syntypes: Originally described by Cragin (1893). Repository likely USNM or UT (BEG). Exact syntype repository uncertain; Cragin did not designate a holotype.
Locality: Sierra Blanca Mountains, El Paso (now Hudspeth) County, Texas.
Stratigraphy: Washita Group (Comanche Series).
SYNONYMY
- Diplopodia streeruwitzi Cragin, 1893
- Tetragramma streeruwitzi (Cragin) Cooke, 1946
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 streeruwitzi (Cragin, 1893)
TYPE SPECIES: Cidarites variolare Brongniart, 1822
DIAGNOSIS
A Tetragramma characterized by a subcircular, very depressed test (flattened above and below). Interambulacra feature a high number of tubercle rows at the ambitus (8 to 10), which reduce significantly aborally. The apical scar is narrow and elongate (Cragin, 1893).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Boracho Formation.
Stratigraphic Units: Upper Cretaceous, Cenomanian.
Counties: Hudspeth (Sierra Blanca), El Paso, Culberson (Kent).
Abundance: Uncommon; confined to West Texas.
DESCRIPTION
TOP: Length, width, height: 36.0 mm L × 11.8 mm H. Top shape: Subcircular to very slightly quinquelateral. Top domed: Decidedly depressed; flattened almost as much above as below (Cragin, 1893). Cragin's syntype was larger (Breadth 44 mm).
SIDE: Ambitus: Ambitus at midpoint. Side shape: Depressed profile.
BOTTOM: Bottom shape: Distinctly flattened; considerably inverted around the peristome.
AMB: Amb shape: Moderate width; straight. Amb arrangement: Two vertical rows of primary tubercles, comparable in size to the central interambulacral rows at the ambitus. Width: Interambulacra are nearly 3 times the width of the ambulacra.
PORE PAIRS: Arrangement: Simple (uniserial) at the ambitus; biserial aborally (toward apical system) and crowded near the peristome. Poriferous zones are wide above the ambitus but narrow at the ambitus (Clark & Twitchell, 1915).
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: Yes. Interambulacral Tubercles: High density at ambitus (6 to 8 rows per Clark; up to 10 rows per Cragin in syntype material). The constituent tubercles decrease in size from the center of the plate outward. Rows gradually disappear aborally.
GRANULES: Distribution: Miliary zone on lower half contains two alternatin rows of small secondary tubercles.
APICAL SYSTEM: Size: Medium. Shape: Apical scar (cicatrix) is narrow and elongate. Features: The posterior angle of the cicatrix forms a capacious, rounded emargination that invades the interambulacral area deeply. (Cragin, 1893).
PERIPROCT (ANUS): (Unknown).
PERISTOME (MOUTH): Size: Small. Lip: Not very large. Buccal margin simple.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype USNM 474149.
ETYMOLOGY
Named in honor of W. H. von Streeruwitz (1833–1916), geologist with the Geological Survey of Texas who collected the type material.
REMARKS & COMPARISONS
Remarks: Cragin (1893) placed this in Diplopodia (a synonym of Tetragramma) and noted its affinity to T. malbosii (of Europe) and T. taffi.
Tetragramma streeruwitzi is one of the most distinctive Texas Tetragramma due to its very depressed test, high number of interambulacral tubercle rows, and narrow, elongate apical scar. The species shows 8–10 rows at the ambitus (depending on author), far exceeding the row counts of Glen Rose and Washita species to the east. The test is flattened above and below to a degree not seen in other Texas forms, and the apical scar is proportionally narrower and more elongate than in any other regional species. The species is confined to far West Texas, occurring only in the Boracho Formation and equivalent Washita units of the Sierra Blanca region. Cragin’s original material was larger than the hypotype figured here, but the depressed profile, high tubercle density, and elongate cicatrix are consistent across all known specimens.
Comparisons:
• Tetragramma malbosii (Europe): T. streeruwitzi is more depressed, with a smaller, narrower, and more elongate apical scar. It also has more interambulacral tubercle rows on the lower half of the test than similarly sized T. malbosii. The European species is more inflated and has a broader cicatrix.
• Tetragramma taffi (Texas): T. taffi is much larger and more inflated, with 8–10 rows but arranged differently and lacking the extreme flattening of T. streeruwitzi. The apical system of T. taffi is broader and not as elongate.
• Tetragramma goodlandense (Texas): T. goodlandense has six rows plus secondary rows, but the test is not nearly as depressed, and the apical scar is wider and more pentagonal. T. streeruwitzi is flatter and has more rows at the ambitus.
• Tetragramma hammerschmidti (Texas): T. hammerschmidti has six rows with high tubercle counts but is moderately inflated, not depressed. Its apical system is round, not elongate.
• Tetragramma glenrosense (Texas): T. glenrosense has only four rows and a more inflated test. The apical system is pentagonal and broader. T. streeruwitzi is far more depressed and has many more rows.
• Tetragramma cranei (Texas): T. cranei is much smaller, with six rows arranged in a 12–9–5 pattern, and has a pentagonal apical system. It lacks the extreme flattening and high row counts of T. streeruwitzi.
