Book Review: Cambrian Ocean World

Cambrian Ocean World: Ancient Sea Life of North America by John Foster (2014)

Cambrian Ocean World: Ancient Sea Life of North America by John Foster
The Cover of Cambrian Ocean World features a lovely painting by John Agnew that reconstructs Middle Cambrian time during deposition of the Spence Shale.

Cambrian Ocean World is a treasure trove of information, general and specific, for the trilobite enthusiast. Although the first fifty or so pages contain the obligatory general discussions/explanations of paleontological, geological, and biological concepts and terminology (and can likely be skipped by those with significant background in the earth and life sciences), the bulk of the book is a detailed march through the stratigraphy, depositional settings, and paleontology of the Cambrian section of North America–with minor digressions to places like Sirius Passet of Greenland.

In general, the book has a density of information similar to that of an undergraduate survey course textbook, and so it would be difficult to summarize its contents in detail. Below find a few snippets of commentary relating to some of the major features/interesting or unusual highlights contained within.

Modocia typicalis, Marjum Formation, Cambrian Period, Millard County, Utah
The elegant Modocia typicalis, Marjum Formation, late Middle Cambrian Epoch, Millard County, Utah. This book describes in some detail the depositional setting and fossils of the Marjum Formation, including the cyclic nature of its deposition. Sediments of the Marjum formation, along with those of many famous trilobite-bearing formations, were deposited along the northern margin of tropical Laurentia as shown in Figure 1.4B of the book. Specimen is 2.0 cm long.

Early in the book, a summary of the Precambrian history of the world includes a lengthy discussion the Ediacaran Period, its unique life forms, and the unresolved question of whether or not these organisms were true animals or represent an unrelated radiation of multicellular life before the dawn of the Cambrian Period. Another early point of interest in the book is a discussion of recently discovered moss spores in the Bright Angel Shale (of Grand Canyon section fame) and the notion that Cambrian terrestrial ecosystems may have also included algae, slime molds, and lichens–very different from the traditional view of the early Paleozoic landscape as being essentially barren.

The heart of the book begins with the appearance of Treptichnus pedum, a circular (in part) trace fossil of world-wide distribution and its preservation of the first complex burrowing/feeding behavior that marks the official beginning of the Cambrian Period. At this point in earth history, though, trilobites are still twenty million years in the future. The sudden appearance, fully formed, of the the oldest trilobites in North America, those of the Fritzaspis Zone of the Montezuma Range in Esmeralda County, Nevada, has led to speculation about soft-bodied trilobites or trilobite-ancestors extending back into the Proterozoic Era and other hypotheses of trilobite origins–ideas discussed by Foster.

Bolaspidella housensis, Wheeler Shale, Cambrian Period, Millard county, Utah
Cluster of Bolaspidella housensis, Wheeler Formation, Middle Cambrian Epoch, Millard county, Utah. The Wheeler Formation has been interpreted is a deep water, outer detrital belt unit deposited in a series of cycles reflecting sea-level rises and falls. Slab is 5.0 cm long.

Chapter 4 begins with an interesting discussion of Early Cambrian reefs. These reefs, composed primarily of archaeocyathids and other exotic organisms likely unrelated to extant reef-forming organisms, will be unfamiliar to most readers. The placement of trilobites in this exotic paleoenvironment is attention-getting and unexpected. Figure 4.3, for example, shows a Cruziana trace within this, what will be for most, weird paleoecological setting.

This middle part of the book also contains a somewhat lengthy discussion of trilobite morphology, taxonomy, stratigraphic distribution, and paleoecology. In addition to the typical discussion of the dorsal exoskeleton, the book explains trilobite nervous, digestive, circulatory, reproductive, and respiratory systems. Interestingly, the book references research suggesting that the outer branch of the trilobite limb (the filamentous branch), which traditionally has been considered a gill, rather was used to push water across the ventral surface for the purpose of respiration.

An important feature of the last half of the book is a series of descriptions of significant Cambrian fossil localities. Among many examples are localities in the Marble Mountains of California, Ruin Wash in the Pioche Shale of Nevada, and the House Range in Utah.

One chapter is devoted entirely to the Middle Cambrian Burgess Shale of British Columbia, a topic familiar to most trilobite enthusiasts. A highlight of the Burgess Shale chapter is a discussion of the functional morphology of the seven species of anomalocarids that occur in the Mount Stephen Trilobite Beds–and the lack of evidence that anomalocarids were the makers of “bite marks” in the dorsal exoskeletons of trilobites. Foster also touches on the potential role of submarine brine seeps in the paleoecology and preservation of fossils in the Burgess deposits. This is a topic not covered in most works for a general audience. Lovely stipple drawings of Burgess animals by Matt Celesky (reminiscent of those by Marianne Collins in Gould’s Wonderful Life) grace this part of the work.

Glyphaspis capella(?), Wolsey Shale, Bear Tooth Lake, Montana
An early asaphid: Glyphaspis capella(?), Wolsey Shale, Bear Tooth Lake, Montana. Like many groups of invertebrates, asaphid trilobites begin their adaptive radiation in the Middle Cambrian. Asaphids are important by the Late Cambrian and a major component of many Ordovician communities. They disappear near the end of the Silurian Period. Specimen is 2.2 cm long.

The concluding sections of the book focus on some technical aspects of paleobiology such as taphonomy, paleoecology, the nature of the Cambrian explosion itself, and the biological legacy of the Cambrian Period. This part of the book will likely challenge readers without significant formal background in paleontology, but are worth slugging though for the committed.

All in all, Cambrian Ocean World, is a wonderful source of information for anyone interested in the Paleozoic Era, even if it is used primarily as a reference and not read cover to cover. Having not worked in the geosciences for many years, this book reminds me just how much work, knowledge, and imagination is involved in trying to understand the fossil record and the life of the past. Foster’s book is certainly not for the vast majority who seek to skate around on the surface of existence, but for those seeking a fuller understanding of life on our planet it offers much to contemplate and appreciate.

@2017 Christopher R. Cunningham. All rights reserved. No text or images may be duplicated or distributed without permission.

Book Review: A Sea Without Fish

A Sea Without Fish: Life in the Ordovician Sea of the Cincinnati Region by David L. Meyer and Richard Arnold Davis (2009)

A Sea Without Fish focuses on the famously fossiliferous Upper Ordovician rocks of the Cincinnati region. As someone who lives in Houston, Texas, surrounded by just about the least interesting geology and paleontology imaginable, descriptions of a landscape bristling with early Paleozoic rocks and fossils inspires a bit of jealousy.

Having grown up on marine Ordovician rocks in southern Minnesota, many of the organisms and lithofacies described in this book are familiar, and remind me just how much I miss being able to simply walk or bike to fossiliferous outcrops that record a period of earth history so wildly different from our own.

The Cover features stunning reconstruction "The Cincinnatian" by John Agnew
The book’s cover features a stunning reconstruction of a marine scene from the Late Ordovician Epoch, “The Cincinnatian,” by John Agnew (2007).

To begin, the book provides the customary general discussion of geological and biological terminology. A somewhat lengthy summary of the history of paleontological exploration of the area is also included. The bulk of the volume surveys the major groups of fossil organisms found in Cincinnatian rocks, from algae to hemichordates and conodonts. Interestingly, the authors also devote significant space to trace fossils, biofacies, depositional paleoenvironments and stratigraphy. It is, therefore, a well-rounded treatment of this fascinating stratigraphic interval and geographic area.

The Ordovician Period included a time when North America was essentially submerged, by some estimates (e.g., Hallam) the high water mark of the Phanerozoic, and the Midwest teemed with marine organisms. Of course, the vast majority of these organisms are now extinct. Ohio and surrounding areas resembled the Caribbean or Persian Gulf more than the Midwest of today. By and large, though, the rocks of the Cincinnatian were likely deposited in water less than 35 m deep. Further, the Late Ordovician Epoch was a time of hurricanes, high atmospheric carbon dioxide, and low oxygen levels. The Midwest was also in the Southern Hemisphere.

Primaspis crossota on bryozoan fragment, Kope Formation,Late Ordovician Epoch, Hamilton County, Ohio. Trilobite is 9 mm long.
A Rare Cincinnatian: The Diminutive Odontopleurid Trilobite Primaspis crossota on a bryozoan fragment, Kope Formation, Late Ordovician Epoch, Hamilton County, Ohio. P. crossota is often associated with bryozoans. Figure 11.6E; F in A Sea Without Fish also shows this trilobite preserved on bryozoans. I suspect that a symbiotic relationship existed between these organisms. Trilobite is 9 mm long.

Chapter 11, the arthropod chapter, along with Chapter 16: “Life in the Cincinnatian Sea,” which contains paleoecological information on facies and units and figured examples of trilobites associated with other organisms (nautiloid living chambers), will be of most interest to trilobite enthusiasts. The broad stratigraphic relationships of the Cincinnatian summarized in Figure 15.1 is also a useful touch.

Flexicalymene retrorsa, Sunset Member, Arnheim Formation, Mt. Orab, Ohio. Trilobite is 3.8 cm long.
A Common Cincinnatian: Flexicalymene retrorsa, Sunset Member, Arnheim Formation, Late Ordovician Epoch, Mt. Orab, Ohio. The only Cincinnatian trilobite the casual collector is ever likely to find in the field. Trilobite is 3.8 cm long.

On to quibbles. I consider the title to be a little odd, focusing on something that is absent (unless you consider conodont animals to be vertebrates or “fish”), rather than what is present. Fishes do not become a major part of the fossil record until the Devonian Period. Ordovician agnathans (“jawless fishes”) do appear in a few places around the world, mostly on Gondwanaland (South America and Australia) and North America (Harding Sandstone of Colorado), but open marine Ordovician rocks are typically free of the remains of anything normally called a “fish” (vertebrates minus tetrapods). I think Cincinnatian rocks are interesting enough, and filled with enough organic remains, to warrant a positive descriptive title based upon what is there, rather than what is not.

One last quibble involves collecting localities. The reader can consult Appendix 1 under field guides for collecting localities where the statement “Localities listed in older guidebooks may no longer be accessible.” Because this book seems to have as its audience serious amateur geologists and fossil collectors, a detailed up-to-date list of localities where enthusiasts can safely and legally collect Cincinnatian fossils would, I think, be appreciated.

One of the things that has soured me on fossil collecting in the past is trying to chase down localities from antiquated references—that and fruitless run-ins with constabulary (who object to fossil collecting even though there is no strictly legal basis for their attentions) and other locals who raise biblical or other silly objections to “outsiders” poking around in their rocks. Once, for example, I was collecting on a road cut in Kansas and was approached by a cop because I was creating a “distraction” that might cause motorists to loose control and wreck their vehicles. But as I was violating no law or ordinance, he had to leave me to my diggings.  Ah yes! Nothing rounds out a hot and dusty day in the field better than a scolding by a creationist or policeman!

All in all, I found A Sea Without Fish to be an interesting and worthy addition to my trilobite library. This volume occupies a place of honor on a shelf next to other excellent recent titles about Paleozoic geology and paleontology such as Foster’s Cambrian Ocean World (2014) and Erwin and Valentine’s The Cambrian Explosion: The Construction of Animal Biodiversity (2013). I highly recommend A Sea Without Fishes for all trilobite lovers, no matter where they live.

Diplichnites, Kope Formation, Late Ordovician Epoch, Mason County, Kentucky. Trace fossil is about 1.5 cm across.
Diplichnites, Kope Formation, Late Ordovician Epoch, Mason County, Kentucky. This book figures and discusses many common ichnotaxa of the Upper Ordovician. It also briefly discusses Seilacher’s ichnofacies concept, in which this specimen would be considered repichnial, a locomotory trace. Trace fossil is about 1.5 cm across.

©2016 Christopher R. Cunningham. All rights reserved. No text or images may be duplicated or distributed without permission.

Book Review: Ordovician Trilobites of Russia

Ordovician Trilobites of the St. Petersburg Region, Russia by V. Klikushin, A Evdokimov, and A. Pilipyuk (2009)

My first reaction to the unboxing of this volume last month was shocked disbelief. Glassy-eyed, I stared in awe as I flipped through the pages, all 541 of them. The amount of work that went into this book must have been nothing short of monumental. And these efforts represent a sort of vertical monopoly: the specimens described were found, excavated, prepared, photographed and discussed by the authors and the associates of the St. Petersburg Paleontological Laboratory during a relatively short period of the recent past.

The odontopleurid trilonite Boedaspis decorates the cover of this volume.
The spectacular odontopleurid trilobite Boedaspis ensifer decorates the cover of this volume.

Although the book makes reference to around 1600 previous works and reproduces illustrations from publications going back two centuries (and in several languages), the heart of the publication is the photographic record of specimens collected during the operation of the aforementioned commercial enterprise. As noted in the introduction, many of the figured specimens now reside in private and museum collections around the world. Professional scientists may object to the lack of  “availability” of specimens for formal study and publication, but for the collector and enthusiast, this work is a cornucopia of information.

Interestingly, the book covers 209 species of trilobites (in 91 genera and 31 families) based, with a few exceptions, on complete specimens only. The authors mention “many” additional species known only from more fragmentary remains to be addressed in a future work. This forthcoming work, should it see fruition, promises to be, in my opinion, even more compelling than the present volume.  What true rarities and oddities exist and are to be revealed?

Chasmops, Ordovician Period, Russia
Chasmops sp., Ordovician Period, Russia. With this volume it will be possible to dig into the collection and double-check initial identifications—and add up-to-date specific assignments. Trilobite is 3.7 cm long.

Interestingly, the book contains a few photographs from the field, primarily quarries. These, plus the map showing 68 trilobite localities in the Ordovician outcrop belt south of St. Petersburg, leave me wondering just what it would be like to go collecting in this part of the world. I grew up collecting fossils in the Ordovician of southern Minnesota, and I have some limited experience collecting in the Cincinnatian, often touted as containing “some of the most fossiliferous rocks in the world.”

But given the sheer volume and quality of Ordovician trilobite specimens available on the commercial market from Russia, I somehow suspect that the Russian deposits are without peer. I remember first walking into dealer rooms at the Tucson fossil show in the early 90’s and being simply flummoxed at the number and quality of specimens available. Only the Lower Devonian of Morocco seems to be as prolific a commercial source of superb trilobite specimens.

Apart from allowing enthusiasts to gawk at pricey, out-of-reach specimens, this book’s most important application, I think, will be in allowing collectors to definitively identify the 28 species of nearly look-alike Asaphus trilobites that are commercially available (and actually in their collections!) and described in great detail, along with biometric data—and likewise for the 20-plus species of Russian illaenids. In the short time I have had this work, I have already found several erroneous identifications in my own collection. I have also found several taxonomic name changes: the spectacular “Cheirurus” specimens, for example, are now placed in Paraceraurus.

Delphasaphus delphinus, Ordovician Period, St. Petersburg region, Russia
Delphasaphus delphinus, Ordovician Period, St. Petersburg region, Russia. Due to a bulbous “nose,” this asaphid is distinctive–but was labelled Asaphus delphinus in my collection. This book allows the collector to make up-to-date taxonomic repairs to their collections. If outstretched, this trilobite would be about 7.5 cm long.

One minor disappointment: This book is about trilobite identification, taxonomy, and morphology, only. There are no references to depositional paleoenvironments or paleoecology, and the volume contains only limited stratigraphic information. I would have enjoyed reading about any paleoecological associations (epibionts, trilobites found in mollusc shells, evidence of predation, trilobites in burrows, etc.) that the authors have undoubtedly encountered in their field work and preparation of specimens. I suspect that these men have a tremendous body of knowledge on these subjects as well.

But this is a quibble. Without question, this is a work that belongs in every trilobite enthusiast’s library. Even if I don’t have a specific question or purpose, I find myself flipping through this book on a nearly daily basis. And it will be years before I can significantly tap the potential for gaining knowledge about trilobites that this work can provide.

Illaenus tauricornis, Ordovician Period, Russia
Illaenus tauricornis, Ordovician Period, Russia. Perhaps the most spectacular and identifiable of the Russian illaenids. The many other species are not so easy. Trilobite is 8.5 cm long.

©2016 Christopher R. Cunningham. All rights reserved. No text or images may be duplicated or distributed without permission.