Stichomicropora baccata (Canu & Bassler, 1926)
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publication ID |
https://doi.org/ 10.1111/j.1096-3642.2005.00179.x |
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persistent identifier |
https://treatment.plazi.org/id/6F0C243F-FF8C-257A-FF26-626B0557FA8C |
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treatment provided by |
Diego |
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scientific name |
Stichomicropora baccata |
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STICHOMICROPORA BACCATA View in CoL ( CANU & BASSLER, 1926)
( FIGS 9A, B View Figure 9 , 22B View Figure 22 , 24F, J View Figure 24 )
Material: USNM 69954 View Materials (syntype suite), Cretaceous , Maastrichtian , Ripley Formation , Coon Creek, McNairy County, Tennessee, USA .
Description: Autozooids have 0–4 oral spines of equal diameter, in most instances two. Examples of intact ovicells show them to be constructed of 3–5 flattened spines of variable width. These spines originate on the salient border between the concave trapezoidal proximal gymnocyst (ovicell floor) and the distal cryptocyst. They are arranged in a gently curved, distally convex arch or in a straight line ( Figs 9A, B View Figure 9 , 24F, J View Figure 24 ). The spines are directed proximally towards the orifice of the maternal autozooid, their edges closely juxtaposed ( Figs 9A View Figure 9 , 22B View Figure 22 ). Each spine has a relatively narrow base ( Fig. 9B View Figure 9 ), broadens rapidly in its middle part and narrows again towards the tip. Ovicell spine bases are oval, roundish or subquadrate in cross-section, and draped with cryptocystal calcification ( Fig. 9B View Figure 9 ). The tips of the spines form a narrow arch-like opening for the ovicell, placed just above the orifice of the maternal zooid ( Fig. 9A View Figure 9 ). Depressions (facets) occur on the cryptocystal frontal shields of the two zooids laterally adjacent to the ovicell ( Fig. 9A, B View Figure 9 ). Each ovicell possesses three openings: the main proximal opening and two lateral foramina above the cryptocystal facets of the lateral zooids. However, cryptocystal facets are not always developed, and in this case the lateral foramina are probably reduced in size. Communication pores connecting the internal coelomic cavities of the spines with the distal zooidal chamber are clearly seen in broken ovicells. It is likely that the lumens of the juxtaposed spines are not confluent.
Remarks: The first description of the ovicells of Stichomicropora baccata (as Micropora baccata sp. nov.) was given by Canu & Bassler (1926: 36, pl. 6, figs 4–6) based on material from the Maastrichtian Ripley Formation of Tennessee, USA. Later, Voigt (1930: 473, pl. 22, fig. 5) depicted broken ovicells in specimens from the Campanian (mucronata Zone) of Rügen, Germany which are likely to belong to a different species. Taylor & McKinney (2002: fig. 1e, f only) restudied the ovicells of the type material.
( FIGS 9C- E View Figure 9 , 24C, F, J View Figure 24 )
Material: NHM BZ4859 , Cretaceous , Maastrichtian , Peedee Formation , Rocky Point Member , Martin Marietta Ideal Quarry , Wilmington , North Carolina, USA, P. D. Taylor Collection. NHM BZ4796 , Cretaceous , Maastrichtian , Prairie Bluff Chalk , adjacent to Lake Ridge Apartments , Livingston, Sumter County, Alabama, USA, P. D. Taylor Collection .
Description: Most autozooids possess four oral spines, although some have five, with the distal spines being the smallest. Ovicells are formed by the distal autozooids. In some colonies all of the zooids over large areas possess ovicells ( Fig. 9C View Figure 9 ), with specific zooids being both maternal and constructing brood chambers for their proximal neighbours. Intact ovicells are constructed of four flattened spines of unequal width. These originate along the elevated border between the concave trapezoidal proximal gymnocyst (ovicell floor) and distal cryptocyst. Ovicell spine bases are arranged in a gently curved arch, either distally convex or concave, or in a straight line ( Figs 9D, E View Figure 9 , 24C, F, J View Figure 24 ). They are directed proximally towards the orifice of the maternal autozooid. Each spine has a relatively narrow base but broadens distally to become closely juxtaposed, possibly even fused, with the adjacent spines. The narrow tips of the spines form the arch-like proximal opening of the ovicell, placed just above the maternal zooid orifice. The outermost ovicell spines are widest, with their outer edges moderately curved ( Fig. 9D, E View Figure 9 ). These edges are positioned just above depressed cryptocystal facets in the frontal walls of the two zooids laterally adjacent to the ovicell. As in S. baccata , lateral foramina are present, forming supplementary openings to the main proximal opening of the ovicell. Broken ovicells clearly expose oval communication pores connecting the cavities of the spines with the chamber of the distal zooid. The broken tips of some ovicell spines show that each has an independent cavity at this level, suggesting that, even though the walls of adjacent spines may perhaps be fused, the lumens of the juxtaposed spines are not confluent.
Remarks: This species was initially regarded as S. baccata by Taylor & McKinney (2002: fig. 1g), but it evidently differs in the flatter shape of the ovicell spines, greater outward curvature of the lateral ovicell spines, and oral spines averaging four rather than two in number.
( FIGS 9F View Figure 9 , 24J View Figure 24 )
Material: NHM BZ4186 , Maastrichtian, Peedee Formation, Martin Marietta Ideal Quarry, nr Wilmington, North Carolina, USA, P. D. Taylor Collection .
Description: Autozooids have 5–7, usually six, oral spines. There are no major differences in the morphology of ovicells from that seen in Stichomicropora sp. 6 described above.
Remarks: This species resembles S. baccata but has ovicells with outwardly bowed lateral spines and generally six rather than two oral spines.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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