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Evactinopora radiata Meek & Worthen, 1865
Mississippian - Osagean Series
Fern Glen Formation
Jefferson County, Missouri

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Evactinopora radiata 1

This specimen shows both the base of a colony and the upper surface of a colony, although they are of different sizes. The larger specimen is exceptional because the upper surface of a mid-sized colony is well exposed. The smaller colony has a pit or depression on the base of the colony that is the most distinct of all the specimens in our collection.

Evactinopora radiata ranging from 4 to 9 rays

Evactinopora radiata 2 Evactinopora radiata 3 Evactinopora radiata 4

Evactinopora radiata 5 Evactinopora radiata 6

Evactinopora radiata 7 Evactinopora radiata 8 Evactinopora radiata 9

Evactinopora radiata 10 Evactinopora radiata 11 12

Evactinopora radiata 13 (9 Rays)  Photo courtesy of Bill Rushlau

A pit or depression in the middle of the base of the colony (specimens#1, #7, #10 and #12) is a fairly common feature and many specimens show a faint depression in that position (specimens #3, #5, #6 and #11). Specimen #9 is an example of larger specimen with no depression in the middle of the star. The pits and depression areas in the center of larger specimens appears to be an original feature. We have seen no evidence that depression features are a result of breakage.

The close-up view of specimen #2 shows a faint round reddish circle in the middle of the star in place of a pit or depression. It appears that the colony covered over some reddish mud present in the area of an original depression by secreting added skeleton onto the base of the colony.

Some colonies (specimen # 7and #10) have sharp raised edges on the rays where they come together in the middle of the star.

Evactinopora collected from other localities
12-14 not in our collection

Evactinopora sp. (9 Rays)
Evactinopora sp. (radiata?)
Reads Spring Limestone
Roaring River State Park
Near Barry, Missouri (West of Branson, Missouri)
Image courtesy of Bill Jacobson
Collected in 1935 when he was 8 yrs old

Evactinopora grandis (grandis with 4 rays)
Evactinopora grandis (4 rays)
Mississippian - Osagean Series
Burlington Formation
Pike County, Illinois
Collected by: Steven Holley
photographed by: Barry Sutton

Evactinopora sp.
Evactinopora sp.
Mississippian - Burlington Limestone
Monroe City, Missouri
Image from Joe Konicki's

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