Polydiadema travisense Smith and Rader, 2009
Plate: PoTr-10
Series: Lower Cretaceous Group: Trinity Formation: Glen Rose
Locale: Canyon Lake County: Comal Stage: Albian
Length: 19.7 mm Height: 7.6 mm
Specimen in photo: NPL 83035 Hypotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: BMNH EE13452 (Natural History Museum, London) (Smith & Rader, 2009).
Locality: Lago Vista, Travis County, Texas.
Stratigraphy: Unit 6, Upper Member, Glen Rose Formation.
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: Polydiadematidae Lambert, 1900
Genus: POLYDIADEMA Lambert, 1888
Species: Polydiadema travisensis Smith & Rader, 2009
TYPE SPECIES: Cidaris mamillana Roemer, 1836
DIAGNOSIS
A species of Polydiadema distinguished by the development of a large secondary tubercle on the adradial side of the primary tubercle on ambital interambulacral plates; this secondary tubercle approaches the primary in size. Adapical interambulacral zones feature a naked, slightly depressed median zone (Smith & Rader, 2009).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Trinity
Formations: Glen Rose Formation (Upper Member).
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Travis, Comal.
Abundance: Common in specific units of the Upper Glen Rose.
DESCRIPTION
TOP: Length, width, height: 19.7 mm L × 7.6 mm H. Top shape: Circular. Top domed: Depressed and flattened aborally.
SIDE: Ambitus: Positioned at midpoint. Side shape: Depressed profile with flattened upper and lower surfaces (Smith & Rader, 2009).
BOTTOM: Bottom shape: Flattened/depressed.
AMB: Amb shape: Straight; pointed at apical system, widening to the ambitus, then narrowing slightly to the peristome. Amb arrangement: Two rows of ~13 tubercles. Plating is trigeminate (diadematoid style) (Smith & Rader, 2009).
Width: At the ambitus, interambulacra are twice the width of the ambulacra; at the apical system, they are three times wider; at the peristome, widths are equal.
PORE PAIRS: Arrangement: Predominantly uniserial around the test. Adorally, pore pairs become offset into triads to form short phyllodes (lowest ~9 pore pairs). Towards the apex, pores may become partially/irregularly offset (Smith & Rader, 2009).
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: Yes. Mamelons: Knob-like. Interambulacral Tubercles: Two rows of 12–13 primary tubercles. Below the ambitus, the rows taper quickly. Secondary Tubercles: Two rows of secondary tubercles become concentrated at the ambitus (about 10 in each row); on ambital plates, the adradial secondary tubercle is prominent and nearly equals the primary in size (Smith & Rader, 2009). Scrobicular Tubercles: Circle the primary tubercles.
GRANULES: Distribution: Interradial zone on ambital plates covered in small secondaries/granules. Adapically, granules are lost from the interradial zone, leaving a naked, slightly depressed area leading to the apical disc (Smith & Rader, 2009).
FASCIOLE: Absent.
INTERAMB: Shape: Plates are much wider than tall at the ambitus.
APICAL SYSTEM: Size: Diameter equal to half (50%) the diameter of the test (Book Author); 40–45% (Smith & Rader, 2009). Shape: Subpentagonal/Pentagonal. Features: Cuts into interambulacra; slightly sunken (Smith & Rader, 2009).
PERIPROCT (ANUS): (Unknown).
PERISTOME (MOUTH): Size: Equal in size to the apical system (~40% of test). Shape: Circular. Lip: Notches moderately deep (sharp/rimmed); lips more pronounced toward interambulacra.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83035.
ETYMOLOGY
Named for Travis County, Texas, the type locality (Smith & Rader, 2009).
REMARKS & COMPARISONS
Remarks: This species co-occurs with Loriolia rosana. It is distinguished from L. rosana by the lack of dense, uniform granulation and the presence of the large secondary tubercle on ambital plates. Loriolia typically has a more elongated apical disc.
Polydiadema is neuter; travisensis is masculine/feminine, name changed to P. travisense.
Comparisons:
Plate: PoTr-10
Series: Lower Cretaceous Group: Trinity Formation: Glen Rose
Locale: Canyon Lake County: Comal Stage: Albian
Length: 19.7 mm Height: 7.6 mm
Specimen in photo: NPL 83035 Hypotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: BMNH EE13452 (Natural History Museum, London) (Smith & Rader, 2009).
Locality: Lago Vista, Travis County, Texas.
Stratigraphy: Unit 6, Upper Member, Glen Rose Formation.
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: Polydiadematidae Lambert, 1900
Genus: POLYDIADEMA Lambert, 1888
Species: Polydiadema travisensis Smith & Rader, 2009
TYPE SPECIES: Cidaris mamillana Roemer, 1836
DIAGNOSIS
A species of Polydiadema distinguished by the development of a large secondary tubercle on the adradial side of the primary tubercle on ambital interambulacral plates; this secondary tubercle approaches the primary in size. Adapical interambulacral zones feature a naked, slightly depressed median zone (Smith & Rader, 2009).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Trinity
Formations: Glen Rose Formation (Upper Member).
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Travis, Comal.
Abundance: Common in specific units of the Upper Glen Rose.
DESCRIPTION
TOP: Length, width, height: 19.7 mm L × 7.6 mm H. Top shape: Circular. Top domed: Depressed and flattened aborally.
SIDE: Ambitus: Positioned at midpoint. Side shape: Depressed profile with flattened upper and lower surfaces (Smith & Rader, 2009).
BOTTOM: Bottom shape: Flattened/depressed.
AMB: Amb shape: Straight; pointed at apical system, widening to the ambitus, then narrowing slightly to the peristome. Amb arrangement: Two rows of ~13 tubercles. Plating is trigeminate (diadematoid style) (Smith & Rader, 2009).
Width: At the ambitus, interambulacra are twice the width of the ambulacra; at the apical system, they are three times wider; at the peristome, widths are equal.
PORE PAIRS: Arrangement: Predominantly uniserial around the test. Adorally, pore pairs become offset into triads to form short phyllodes (lowest ~9 pore pairs). Towards the apex, pores may become partially/irregularly offset (Smith & Rader, 2009).
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: Yes. Mamelons: Knob-like. Interambulacral Tubercles: Two rows of 12–13 primary tubercles. Below the ambitus, the rows taper quickly. Secondary Tubercles: Two rows of secondary tubercles become concentrated at the ambitus (about 10 in each row); on ambital plates, the adradial secondary tubercle is prominent and nearly equals the primary in size (Smith & Rader, 2009). Scrobicular Tubercles: Circle the primary tubercles.
GRANULES: Distribution: Interradial zone on ambital plates covered in small secondaries/granules. Adapically, granules are lost from the interradial zone, leaving a naked, slightly depressed area leading to the apical disc (Smith & Rader, 2009).
FASCIOLE: Absent.
INTERAMB: Shape: Plates are much wider than tall at the ambitus.
APICAL SYSTEM: Size: Diameter equal to half (50%) the diameter of the test (Book Author); 40–45% (Smith & Rader, 2009). Shape: Subpentagonal/Pentagonal. Features: Cuts into interambulacra; slightly sunken (Smith & Rader, 2009).
PERIPROCT (ANUS): (Unknown).
PERISTOME (MOUTH): Size: Equal in size to the apical system (~40% of test). Shape: Circular. Lip: Notches moderately deep (sharp/rimmed); lips more pronounced toward interambulacra.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83035.
ETYMOLOGY
Named for Travis County, Texas, the type locality (Smith & Rader, 2009).
REMARKS & COMPARISONS
Remarks: This species co-occurs with Loriolia rosana. It is distinguished from L. rosana by the lack of dense, uniform granulation and the presence of the large secondary tubercle on ambital plates. Loriolia typically has a more elongated apical disc.
Polydiadema is neuter; travisensis is masculine/feminine, name changed to P. travisense.
Comparisons:
- Polydiadema rotulare: P. travisensis resembles P. rotulare (Aptian of Europe/Mexico) but is immediately distinguished by the large adradial secondary tubercle on the ambital plates (Smith & Rader, 2009).
- Phymosoma texanum: Distinguished by having perforate tubercles (vs. imperforate in Phymosoma) (Smith & Rader, 2009).
