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Compare Orthoseira oregoniana

Danz and Kociolek 2022

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Orthoseira oregoniana is similar to taxa within the O. roeseana complex (Houk 1993). Briefly, group “tatrica” has spathulate spines while O. oregoniana has simple spines, group “epidendron” has many more carinoportulae (2–7), and group “dendrophila” is smaller (8–29 µm in diameter).

Orthoseira oregoniana is most easily confused with O. tropica and O. ursula due to the presence of ridge features near the margin. Note that O. oregoniana has been documented within the contiguous United States, while O. tropica and O. ursula have only been reported from South America. Orthoseira oregoniana striae begin to branch at the margin with the mantle, while the other two taxa have striae that begin to diverge on the valve face. Orthoseira ursula is larger (40–65 µm) and has additional structure or ornamentation in the space between carinoportulae.


LM scalebar = 10 µm
Orthoseira oregoniana LM2 Orthoseira oregoniana LM4 Orthoseira oregoniana LM5 Orthoseira oregoniana LM1 Orthoseira oregoniana LM3 Orthoseira oregoniana LM6
Diameter
19.7-46.9 µm
Striae in 10 µm
4.1-5.3

Orthoseira roeseana

(Rabenh.) Pfitzer 1871

Orthoseira roeseana LM1 Orthoseira roeseana LM2 Orthoseira roeseana LM3 4 674 30 6 Ortho Roes 715 A 5Rep 491 22 3 Ortho Roes 715 A
Diameter
22.1-50.5 µm
Striae in 10 µm
6.4-7.1 based on circumferential density

Also compare to

Orthoseira ursula

Metzeltin and Lange-Bert.

Orthoseira tropica

(Krasske) Metzeltin and Lange-Bert.

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