Table 2 (continued on next two pages). Key characters of all species currently placed in the genera Ophiomitrella Verrill, 1899 and Ophiosemnotes Matsumoto, 1917, compiled from original descriptions, examinations of type specimens or photos of type material, and Paterson (1985). Abbreviations: AS = adoral shield; DD = disc diameter; OS = oral shield. Generic type species indicated by asterisk.

Species	DD (mm)	Disc spines	Radial shields	Oral shields	Adoral shields
Group A: disc spines low, more or less spherical, or absent
Ophiomitrella americana Koehler, 1914	6.5	small round, with thorny tips	small, 1/₈ of dd, round, widely separated	rhombic, proximally acute, ~2× as wide as long, larger than AS	narrow crescent, proximal to OS
Ophiomitrella araucana Castillo-Alárcon, 1968	9	small granules	1/6 of dd, triangular, distally connected	rhombic, larger than AS	narrow crescent, proximal to OS
Ophiosemnotes brevispina (H.L. Clark, 1911)	8	none	~1/6 of dd, rounded, widely separated	rhombic to pentagonal	trapezoid
Ophiomitrella cordifera (Koehler, 1896)	4	few, low, globular, short peduncle	1/4 of dd, oval to triangular, distally connected	rhombic, proximally acute, larger than AS	crescent, extend barely around OS
Ophiosemnotes diaphora (H.L. Clark, 1911)	11	round granules	1/4 of dd, oval, widely separated	pentagonal, smaller than AS	trapezoid, proximal to OS
Ophiomitrella globulifera (Koehler, 1896)	11	large, globular	1/5 of dd, oval, widely separated	pentagonal to rhombic, large, distal projection	large, trapezoid, curved, proximal to OS
Ophiomitrella granulosa (Lyman, 1878)	9	dense, small granules	small, distally connected	rounded triangular, smaller than AS	large, trapezoid, proximal to OS
Ophiomitrella mensa O’Hara & Stöhr, 2006	10	capitate stumps	1/4 of dd, triangular, contiguous	small, wider than long, pentagonal	trapezoid, larger than OS, proximal to OS
Ophiomitrella nudextrema (H.L. Clark, 1939)	3	trifid stumps	1/6 of dd, triangular	diamond-shaped	trapezoid, large
Ophiomitrella parviglobosa O’Hara & Stöhr, 2006	4	spherical granules	1/9 of dd, triangular to circular	rhombic	crescent, proximal to OS
Ophiomitrella suspectus (Koehler, 1922)	8	dense, club-shaped, pediculate globules	1/5 of dd, triangular, connected	rhombic	trapezoid, large, proximal to OS
Ophiomitrella tenuis (Koehler, 1904)	5–6	dense, small, thorny, elongated granules	1/6 of dd, triangular, separated	rounded rhombic, larger than AS	crescent to trapezoid, proximal to OS
Ophiomitrella thuyi sp. nov.	4.2	smooth, spherical granules, variable size	1/4 of dd, rounded triangular, separated	rounded triangular, small distal lobe, smaller than AS	trapezoid, proximal to OS
Group B: disc spines stellate
Ophiomitrella mutata Koehler, 1904	10	dense, trilobed stumps	1/10 of dd, triangular, widely separated	rounded, rhombic, distal lobe	narrow crescent, proximal to OS
Ophiomitrella polyacantha (H.L. Clark, 1911)	6	stellate stumps, crown with perpendicular thorns	1/6 of dd, triangular, widely separated	rhomboid, proximally acute	trapezoid, proximal to OS
Ophiomitrella sagittata Koehler, 1922	9	dense, strong, trilobed head	1/7 of dd, triangular, widely separated	arrowheadshaped, separating AS	crescent to trapezoid, proximo-lateral to OS
Ophiomitrella stellifera Matsumoto, 1917	4	stellate stumps, crown with 6 thorns	1/10 of dd, triangular, separated	rhombic to arrowheadshaped, larger than AS	trapezoid, proximal to OS
Ophiomitrella subjecta Koehler, 1922	9	dense, short, club-shaped, thorny head	1/9 of dd, triangular, separated	rhombic, proximally acute	narrow crescent, proximal to OS
Group C: disc spines elongated stump-like with thorns
Ophiomitrella barbara Koehler, 1904	7	long stumps with thorny crown	as disc scales, widely separated	rhombic, proximally acute	narrow crescent, proximal to OS
Ophiomitrella chilensis Mortensen, 1952	5	thorny stumps	~1/8 of dd, triangular, distally connected	rhombic, distal lobe	trapezoid, extending around OS
Ophiosemnotes clavigera (Ljungman, 1865)	6.5	long and short thorny stumps	rounded separated	rhombic	trapezoid
Ophiosemnotes conferta (Koehler, 1922)	6	elongated thorny stumps	1/4 of dd triangular, halfway connected	rounded rhombic, larger than AS	crescent, proximal to OS
Ophiosemnotes corynephora (H.L. Clark, 1911)	8	cylindrical stumps	~1/6 of dd, rounded triangular	rhombic	trapezoid, proximal to OS
Ophiosemnotes hamata (Mortensen, 1933)	4	cylindrical stumps	rounded triangular, distally connected	rhombic, larger than AS	crescent, proximal to OS
Ophiosemnotes ingrata (Koehler, 1908)	4	low stumps	1/10 of dd, round, widely separated	rounded rhombic	crescent, proximal to OS
Ophiosemnotes pachybactra (H.L. Clark, 1911)	11	club-shaped stumps	~1/6 of dd, rounded triangular, distally connected	rounded rhombic, as large as AS	crescent to trapezoid, proximal to OS
Ophiosemnotes paucispina (H.L. Clark, 1911)	10	rounded granules	1/6 of dd, oval, widely separated	rhombic	trapezoid
* Ophiosemnotes tylota (H.L. Clark, 1911)	10	stout thorny stumps	1/6 of dd, rounded triangular, distally connected	rhombic	trapezoid, proximal to OS
Group D: bar-like radial shields
* Ophiomitrella laevipellis (Lyman, 1883)	4.5	scattered low granules	pear-shaped (distal ends), bar-like ridge in disc	rhombic to triangular, smaller than AS	trapezoid to crescent, proximal to OS
Ophiomitrella porrecta Koehler, 1914	6.5	dense multifid spines	small as scales (distal ends), widely separated	pentagonal	crescent, proximal to OS