- C1 Sequence (McMicken: Southgate)
- C2-C3 Sequences
- C4-C5 Sequences
- type-A is found in the McMicken and Southgate;
- type-B is found throughout the Cincinatian;
- type-C is found throughout the Richmondian (C4-C6 Sequences) per Osgood, 1970.
Identification in Hand Sample
- General morphology: Branching tunnels
- Branching: Small angles
- Surface ornamentation: None
- Fill: None
- Lining: None
- Spreiten: None
- Substrate: Softground
- Oxygen content: Low-moderate
- Nutrient content: Low-moderate
- Energy: Low
- Behavior: Deposit feeding
- Tracemaker: Sipunculid, marine worm
- Fully marine
Chondrites from the Fairview Formation of Clermont, Ohio (left, MUGM 29432); Chondrites “type C” from the Waynesville Formation of Spring Valley, Ohio (right, OUIP 1734)
Holland, UGA Strat Lab (2013):
- Form dense, interwoven network; surface of burrows marked by delicate longitudinal striae
Buthotrephis gracilis and Buthotrephis ramulosus have been reported from the Cincinnatian, but Osgood seems to have regarded them as Chondrites.
- Description: Large complexes of small root-like tunnels and shafts in dendritic patterns. Usually, burrows never cross, except by a different Chondrites system. Sometimes, look like bird feet. Form along bedding planes.
- Interpretations: Fodinichnia: Feeding burrows of a deposit feeding worm organism; fully marine conditions perhaps indicative of low oxygen zones; sipunculid or marine worm organism similar to modern polychaetes .
Fossils of Ohio (2006):
- Chondrites are composed of a system of branching tunnels. Most of the tunnels are horizontal or nearly horizontal, commonly paralleling bedding. Individual tunnels typically range in width from 1 to 7mm. Size is generally consistent in the same system of tunnels. Osgood (1970, p.328)noted that Chondrites is one of the most common “fucoids”. In Ohio, Chondrites is common in Ordovician rocks of the Cincinnatian Series and can also be found in younger rocks, including Silurian rocks of western Ohio, the Devonian Ohio Shale in northeastern Ohio and in a north-south band in the middle of the state, and the Mississippian Logan Formation east of the Ohio Shale. Chondrites probably represents the work of sediment feeding worms. Osgood (1970) distinguished several types of Chondrites by letter (such as A, B, and C).
Treatise on Invertebrate Paleontology, Part W, Miscellanea Supplement 1 (1975):
- ““Form genus” in widest possible sense; plantlike dendritic patterns of small cylindrical ramifying tunnel systems; individual tunnels neither crossing each other nor interpenetrating (perhaps only between tunnels of different systems); one or few main axes open to surface; branching tunnels trending downward across bedding and then (at least their distal portions) mostly lying parallel to bedding planes; may branch in regular or irregular patterns (highly variable); angle of branching may also be variable or constant, between 25 and 40o; branches may be arranged in pinnate or radial patterns or form compact groups; diameter of tunnels 0.5 to 5 mm, remaining constant within entire tunnel system; otherwise varying from large to small; some tunnels with transversely built-in ellipsoidal pills (their probably fecal origin doubted); preservation of fillings of tunnels controlled by stratinomic factors.” W. Hantzschel, 1975
- Trace fossil nature convincingly proved first by Richter (1927a, 1931), though earlier Nathorst (1881a) and Fuchs (1895) had rejected the former interpretation as algae; producer unknown, perhaps worms. Simpson (1957) suggested sipunchuloid worms working from fixed center on the surface of sediment and producing tunnels by an extensible proboscis; branching pattern may be affected by phobotaxis (Richter, 1927a, p. 218; 1928, p. 226; 1931), p 302); ethological interpretation is still discussed but Chondrites undoubtedly belongs to Fodinichnia and is to be regarded as feeding structures of sediment-eating animals (Richter, 1927; Seilacher, 1955; Osgood, 1970) and not dwelling burrows of filter feeding annelids (Tauber, 1949); detailed studies of the ichnogenus would certainly lead to several additional “new ichnogenera”; some dozens of “ichnospecies” have been described but recognition of these within Chondritesvery difficult (Osgood, 1970, p. 489); for historidal account of many theories of the nature of Chondrites, detailed treatments, and literature see especially Simpson (1957) and Osgood (1970, p. 328-331); for discussion and various reconstructions of tunnel systems of this form see Richter (1921, p. 301 fig. 2), Tauber (1949, p. 149-150, fig 1,2), and Simson (1957, p. 484, fig 2.)