Monterey Formation : Macroalgae

Bruce Parker and E. Yale Dawson published a paper in 1965 describing one of the best preserved and most diverse collections of Cenozoic non-calcareous algae. Calcareous algae are quite common as fossils; their calcium-based skeletons are readily preserved. Algae without such skeletons, however, are rare as fossils, and so a paper presenting a collection of 22 species in ten genera is rather remarkable, especially when you consider that twenty of the species had never before been described.

Most of the material is preserved in diatomite, the accumulations of the skeletons from numerous microscopic diatoms which have been compressed into a light chalk-like rock. A few of the fossils have been preserved in concretionary silty sand. The algae are often preserved alongside the skeletons of ancient fish, and it was because of this that the algae were first discovered.

The entire collection of specimens described by Parker and Dawson, along with related material, was given to UCMP by the Los Angeles County Museum of Natural History in 1990 and now resides in our paleobotanical type collections.

Green and Red Algae

Caulerpites denticulata - a green alga.

This genus includes fossil algae resembling the living green alga Caulerpa. There are several fossils from the Cenozoic which have been so described, as well as some less certain Mesozoic and Paleozoic fossils. Parker and Dawson consider this only provisionally to be a green alga, noting that similar morphologies occur in red and brown algae.

Chondrides flexilis - a red alga.

This is one of the specimens preserved in conretionary sand. The overall growth form resembles members of the Gigartinales, in the red algae.

Paleosiphonia oppositiclada - a red alga.

This alga was preserved with a filament prominent in the central stalk. The specimen also contains fossil fishes.

Brown Algae (kelps)

Julescraneia grandicornis

This is one of the more exciting finds -- a portion of what appears to be a relative of bull kelp. Both Pelagophycus and Nereocystis have a branching morphology like this.

Paleocystophora subopposita

Paleocystophora includes those fossil kelps which are in the Cystoseiraceae, but for which no vesicular branches are known, that is, no reproductive structures.

Paleohalidrys californica

Fossils of Paleohalidrys may be more than 50 cm long. This particular species was originally described from a specimen which lacked vesicles, but new material from the Monterey Formation demonstrated the suspected reproductive structures.

Paleohalidrys occidentalis

This is the upper vegetative portion of one plant. The resemblance to the growing tip of extant Cystoseira is quite remarkable. This is another specimen from concretionary silty sand.

Paleohalidrys superba

Preserved in concretionary sand, the detail of the frond is unusually fine.