-Species Descriptions-

Amplexograptus sp. Elles and Wood, 1907 – Description from Mitchell, 1987

Description: Thecae are amplexograptid with short, slightly outwardly inclined supragenicular walls, a sharp geniculum bearing a genicular flange, and cuspate thecal apertures horizontal to slightly everted. Rhabdosomes may be partly septate, with th31 or some later theca dicalycal, but are more commonly aseptate. Paired antivergellar spines are generally present on dorsal margin of sicular aperture. Th11 invariably bears a subapertural or mesial spine but th12 commonly does not.

Ecology: Planktonic or epiplanktonic.

  Amplexograptus sp., MCZ 146482 Amplexograptus sp., MCZ 146481    
MCZ 146482: 3mm wide
MCZ 146481: 3mm wide

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  Corynoides americanus? (Ruedemann) – Description from Riva, 1974

Corynoides curtus Lapworth. Ruedemann, 1908, p. 240-241, text-fig. 140-144, pl. 13, fig. 4, 17-21; Strachan, 1949, p. 155, 157, 158.
Corynoides curtus var. comma Ruedemann, 1908, p. 242, text-fig. 145-148, pl. 13, fig. 5, 22-24.
Corynoides calicularis var. americana Ruedemann, 1947, p. 359-360, pl.59, fig. 26-29.
Corynoides comma Ruedemann, 1947, p. 360, pl. 58, fig. 49-55; Strachan,1949, p. 155.
Corynoides americanus (Ruedemann). Riva, 1974, p. 37, fig. 10.

Description: Rhabdosomes are thin and short, consisting of gently to strongly curved sicula, from 3.5 to 6.5 mm long, and of a theca originating near the apex of the sicula and growing down on the convex side to about 0.4-0.5 mm from the sicular aperture where it diverges from the sicula. A second theca is seen in some specimens to form near the apex of the first theca. Both the sicula and th1 develop a lamelliform virgellar processes. Growth bands are recognizable in pyritized specimens and they characteristically curve forwards toward the virgellar structure. The edges of the sicular aperture and the virgella are reinforced by secondary thickening as are the aperture and the virgellar structure of the first theca.

Ecology: Planktonic or epiplanktonic.

          Corynoides americanus?, MCZ 146501              
MCZ 146501: 1mm long

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  Corynoides sp. Nicholson, 1867 cf. C. curtus – Description from Bulman, 1970

Description: Rhabdosomes consist of sicula with broad lamelliform virgella and 2 adnate thecae bearing broad apertural processes. Where a third theca occurs, it is small and isolate.

Ecology: Planktonic or epiplanktonic.


          Corynoides sp., MCZ 146502              
MCZ 146502: 1mm long

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  Dicranograptus nicholsoni Hopkinson, 1870 - Description from Ruedemann, 1947

Dicranograptus nicholsoni Hopkinson, 1870, p. 357, pl. 10, fig. 3; Lapworth, 1876, p. 6, p. 3. fig. 79; 1877, p. 141, pl. 7, fig. 2. Tullberg, 1882, p. 20; Gurley, 1896, p. 297; Elles and Wood, 1904, p. 171, pl. 25, figs. 1a-h. Hall, T.S., 1905, p. 24, pl. 6, fig. 7; 1906, p. 274; Ruedemann, 1908, p. 317-320, text-figs. 239-242, pl. 20, figs. 3-5, pl. 21, fig. 1; 1912, p. 79; 1925, p. 52; 1925, p. 53-54; 1947, p. 391, pl. 66, figs. 5-11; Bassler, 1915, p. 416; Ruedemann and Laverdiere, 1935, p. 8.
Dicranograptus cf. nicholsoni Decker, 1936, p. 307; Bulman, 1931, p. 92; Keble and Benson, 1939, p. 78.

Description: Rhabdosomes consist of a short biserial portion (uniformally 5 mm long, with variations to 4 to 6 mm) and long uniserial branches, attaining a length of 130+ mm and forming an axillary angle that varies from 25 to 80 degrees, in majority of specimens lies between 40 to 60 degrees. Branches are frequently straight, but gently curved, either first concave and then convex from beginning, so as to reapproach distally. The biserial section begins narrow (initial width 0.7 mm), but widens to 1.7 mm. The uniserial section branches uniformly 1 mm thick, in some long branches widening gradually to 1.2 mm. Sicula measure 1-1.1 mm, furnished with a short virgella. From its apical end a dividing septum proceeds, and only the first four thecae grow alternately. The biserial section consists of 5 to 6 thecae. Thecae have convex outer walls, which in the biserial section are furnished with strong mesial spines. They overlap about half their length and their apertural parts are introverted and introtored and contained in or almost filling round excavations that occupy fully a third or more of width of branch.

Ecology: Planktonic or epiplanktonic.


          Dicranograptus nicholsoni, MCZ 146506                    
MCZ 146506: 15mm long

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  Geniculograptus typicalis (Hall, 1865) – Description from Berry, 1971

Climacograptus typicalis Hall, 1865, p. 57, pl. A, figs. 1-9; Walcott, 1884, p. 34; Ulrich, 1888, p. 183; Walcott, 1890, p. 339; Winchell and Schuchert, 1895, p. 82, fig. 4; Gurley, 1896, p. 298; Roemer and Frech, 1897, p. 612; Ruedemann, 1901, p. 523, Nickels, 1902, p. 68; Ruedemann, 1908, p. 407-411, text-figs. 354-362, p. 28, figs. 6-7; Bassler, 1915, p. 238; Ruedemann, 1925, p. 59; Decker, 1933, p. 1416; 1934, p. 322; Ruedemann, 1947, p. 440-441, pl. 75, figs 27-38; Berry, 1971, p. 637.
Climacograptus cf. typicalis Decker, 1936, p. 307.
Geniculograptus typicalis (Hall, 1865). Mitchell, 1987, p. 381.

Description: Rhabdosomes are up to 5.5 mm long. They widen from 0.5-0.7 mm at the first thecal aperture to 1.3-1.5 mm at 5 mm from that position, and to their maximum width of 2.0-2.1 mm at 10 to 17 mm from that position. The thecae number 7 to 7.5 in the proximal 5 mm, 15 in the proximal 10 mm, and 10 to 11 in 10 mm in the distal part of the rhabdosome. The supragenicular parts of the free ventral walls are parallel with the rhabdosome axis and apertures are horizontal. The thecae in medial and distal parts of the rhabdosome overlap approximately one-third their length and their apertural excavations occupy one-fourth the width of the rhabdosome. The rapidly tapering aspect of the proximal end of the rhabdosome and the relatively narrow thecal apertural excavations characterize this species.

Ecology: Planktonic or epiplanktonic.


          Geniculograptus typicalis, MCZ 146505              
MCZ 146505: 10mm long (rough estimate)

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  Normalograptus mohawkensis (Ruedemann) - Description from Goldman and Mitchell, 1994

Diplograptus (Mesograptus) mohawkensis Ruedemann, 1912, p. 80-81, text-figs. 19-20, pl. 2, figs. 18-19; Ruedemann, 1947, p. 419-420, pl. 71, figs. 24-28.
Climacograptus mohaawkensis (Ruedemann). Walters, 1977, p. 937-938, pl. 2, figs. f, h, i.
not Climacograptus mohawkensis (Ruedemann). Williams, 1982, p. 246-247, fig. 10e-j.
Normalograptus mohawkensis (Ruedeman). Goldman and Mitchell, 1994, p. 97, pl. 1, figs. J-N, pl. 3, figs. A-B, fig. 4R.

Description: The rhabdosome is short, generally less than 15 mm in length. Thecae are climacograptid, numbering 7.5-8.0 in the first 5 mm, decreasing to 7 in 5 mm distally. Narrow rhabdosomes widen gradually. Inter-aperture widths increase from 0.4-0.5 mm at the first thecal pair to a maximum width of 0.75-0.85 mm at the ninth thecal pair. Thecae are geniculate, but lack genicular flanges. Supragenicular wall straight to gently convex, inclined slightly to the rhabdosome, and approximately 0.4 mm high at the th21, increasing to 0.5-0.55 mm distally. Th11 and th12 are relatively long compared to the next few thecae. Thecal apertures are everted proximally, become horizontal distally, and lack well-developed selvages. The rhabdosome generally becomes septate at the base of the sixth thecal pair, although considerable variation is observed in the level of septal insertion. The proximal end structure corresponds to a Pattern H primordial astogeny (Mitchell, 1987). The sicula is relatively short (approximately 1.0 mm) and broad and bears only a short virgella. The proximal end is narrow and fusiform with the virgella slightly incurved across the sicula aperture. The metathecae of th11 is tightly upturned and has a complete dorsal wall.

Ecology: Planktonic or epiplanktonic

          Normalograptus mohawkensis, MCZ 146499              
MCZ 146499: 7.5mm long

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Orthograptus quadrimucronatus (Hall, 1865) - Description from Goldman, 1995

Graptolithus quadrimucronatus Hall, 1865, p. 144, pl. 13, fig. 1-10.
Diplograptus quadrimucronatus (Hall). Lapworth, 1877, p. 133, pl. 6, fig. 20.
Diplograptus (Orthograptus) quadrimucronatus (Hall). Elles and Wood, 1907, p. 223, pl. 28, fig. 1a-1d, text-fig. 145a-f.
Diplograptus foliaceus gorrelensis Caley, 1936, p. 66, fig. 2.
Glossograptus quadrimucronatus (Hall). Ruedemann, 1947, p. 452 (partim), pl. 78, figs. 1, 2, 6-31 (not figs. 3-5), pl. 79, figs. 1-10, 12-27 (not fig. 11), pl. 81, figs. 29-32.
Orthograptus quadrimucronatus quadrimucronatus (Hall). Goldman, 1995, p. 525, fig. 10.1-10.19, 11.1-11.6, 15.1-15.5, 17.5-17.9 [see for full synonymy]; Goldman and Bergstrom, 1997, p. 999, text-figs. 2l-n, 14e-f.

Description: Rhabdosomes widen from a mean width (excluding apertures) of 1.03 mm at first thecal pair to 1.68 mm at tenth thecal pair, generally parallel sided thereafter. Thecae are inclined to rhabdosome axis at an angle of 20-35 degrees, and free ventral thecal lengths average 0.60 mm proximally, increasing to 0.86 mm distally. The th11 has an apertural spine and th12 has a subapertural spine. The length of unenclosed sicula averages 1.15 mm and the total length is not known in flattened material. The mean width of the sicula aperture is 0.46 mm. Rhabdosomes are separate and bear no unusually long thecal spines.

Ecology: Planktonic or epiplanktonic.


    Orthograptus quadrimucronatus, MCZ 146495 Orthograptus quadrimucronatus, MCZ 146496 and MCZ 146497    
MCZ 146495: 15mm long
MCZ 146496 and MCZ 146497: 16mm long (bottom segment)

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Orthograptus rivai Goldman and Mitchell, 1994 - Description from Goldman and Mitchell, 1994

Orthograptus rivai Goldman and Mitchell, 1994, p. 95, pl. 2, figs. a-h, figs. 4P, 4Q, 5B, 5D; Goldman, 1995, p. 535, figs. 15.15, 15.16.

Description: Rhabdosomes narrow (maximum 1.3 mm) parallel sided; thecae orthograptid, th11 with apertural spine , th12 with subapertural spine, remaining thecae with short paired apertural spines. This species can be differentiated from Orthograptus quadrimucronatus by its much narrower, aseptate rhabdosome. Orthograptus rivai also commonly forms synrhabdosomes.

Synrhabdosomes are enigmatic associations of several individual colonies attached either by their nema or, in a few rare cases, by the virgella. The individual nema are intertwined and may have been fused together. Ruedemann (1895, 1904, 1908, 1947) reconstructed float-associated structures based on Mohawk Valley specimens like these, and although his illustrations have been widely reproduced, such structures have never been found in any subsequent fossils. Synrhabdosomes have been found in a disparate suite of graptolite species and occur commonly in a few species (such as Orthograptus rivai), but most species have never been found to form synrhabdosomes. The biological significance of these associations is controversial. They may be breeding or feeding assemblages, or may be preservational artifacts, but the majority view favors feeding assemblages (Gutiérrez-Marco and Lenz, 1998).

Ecology: Planktonic or epiplanktonic.

          Orthograptus rivai, MCZ 146491 and MCZ 146493              
MCZ 146491 and MCZ 146493: 21mm wide and 16mm wide

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  Rectograptus amplexicaulis (Hall, 1847) - Description from Riva, 1974

Graptolites amplexicaule Hall, 1847, p. 79-80, 316, pl. 26, fig. 11a-b
Diplograptus amplexicaule (Hall, 1847). Hall, 1867, p. 24, 233, pl. 3, fig. 6-7.
Diplograptus (Glyptograptus) amplexicaulis Hall. Ruedemann, 1908, p. 361-365, text-fig. 302-403, 305-306?, 307, pl. 25, fig. 11, 13, 10?,12?
Diplograptus (Amplexograptus) amplexicaulis Hall. Ruedemann, 1947, p. 411-412, pl. 70, fig. 1-4, 7-9, 5-6?, 10-13?,
Orthograptus truncates var. intermedius Elles and Wood. Berry, 1960, p. 92, pl. 17, figs. 4-5.
Orthograptus aff. O. truncates (Lapworth). Berry, 1960, p. 91-92.
Orthograptus amplexicaulis (Hall). Riva, 1969, fig. 3a; Riva, 1974, p. 29, pl. 2, fig. 7-10, text-fig. 9.
Rectograptus amplexicaulis (Hall). Chen et al., 2000, p. 290, fig. 7.21, 8.5.

Description: Rhabdosomes attain several cm in length, widening from 0.8 to 1 mm at the level of th12 aperture to 2-3.5 mm. The maximum width may be attained in 1 cm from the proximal end or very gradually, almost imperceptibly, with all variations in between, and is generally maintained, although some rhabdosomes tend to narrow distally. Thecae alternate, twelve to sixteen proximally, ten to twelve distally; they overlap about three-fifths proximally and seven-tenths distally and are inclined about 30 to 50 degrees to the axis of the rhabdosome, the smaller inclination being typical of proximal thecae. Thecae consist of cylindrical tubes with simple apertures inclined about 30 degrees from the vertical. Apertural excavations are shallow distally, but deeper and more pronounced proximally, and delimited by a selvage merging the thecal aperture with the suprangenicular wall. The proximal end bears a mesial spine on th11, the virgella, and one visible sicular spine. The sicula is 2 to 2.5 mm long and exposed for 1 mm on the obverse side of the rhabdosome. The rhabdosome is circular to ovoid in cross-section, but if the periderm has collapsed it may have a roughly rectangular cross-section or be so depressed along the axis as to appear concave. A thread-like nema extends from the apex of the prosicula through the rhabdosome and for a short distance beyond. The rhabdosome is aseptate.

Ecology: Planktonic or epiplanktonic.


Rectograptus amplexicaulis, MCZ 145785   Rectograptus amplexicaulis, MCZ 145786   Rectograptus amplexicaulis, MCZ 145787
MCZ 145785: 22.5mm long
MCZ 145786: 15mm long
MCZ 145787: largest is19mm long
          Rectograptus amplexicaulis, MCZ 145788                    
MCZ 145788: 18mm long

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