SJF Miscellany

by Carl Strang

There has been a gradual buildup of photos from my monitoring excursions at St. James Farm, and it’s time to empty the bin. Some are pictures of birds.

Ruby-crowned kinglets have been common migrants around the forest edges.

Ruby-crowned kinglets have been common migrants around the forest edges.

A pair of adult red-tailed hawks frequently patrols the sky overhead.

A pair of adult red-tailed hawks frequently patrols the sky.

This juvenile red-tail was tolerated or unnoticed by the residents as it perched near the preserve’s boundary on Sunday.

This juvenile red-tail was tolerated or unnoticed by the residents as it perched near the preserve’s boundary on Sunday.

These young red-tails often are naïve and approachable. This was one of the first photos I took, from just a few yards away. I had to back off to get the entire bird in the frame for the previous photo.

These young red-tails often are naïve and approachable. This was one of the first photos I took, from just a few yards away. I had to back off to get the entire bird in the frame for the previous photo.

Proper awareness in monitoring includes looking in all directions and all size scales.

A small mushroom and moss growing on a fallen log.

A small mushroom and moss growing on a fallen log.

Elsewhere on the same log, a raccoon left a record of its passing. Its five toenails left characteristically spaced scratches when it leaped up to the log. It did not gain purchase here, so either fell back to the ground or otherwise had enough momentum and grip to gain the log.

Elsewhere on the same log, a raccoon left a record of its passing. Its five toenails left characteristically spaced scratches when it leaped up to the log. It did not gain purchase here, so either fell back to the ground or otherwise had enough momentum and grip to gain the log.

Building the story of a preserve also means looking for clues to the landscape’s human history.

These corroding pieces of metal slowly are being engulfed by the continued growth of this tree. They are 30 feet above the ground. At some point I hope to learn the story here.

These corroding pieces of metal slowly are being engulfed by the continued growth of this tree. They are 30 feet above the ground. At some point I hope to learn the story here.

Accumulating experiences of an area’s beauty and blemishes leads to an internal transformation: falling in love with a place.

 

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Sound Ideas: Fun Gus’ Song

by Carl Strang

We’re in the season we associate with death and decay. My own personification of this quality is a character named Fun Gus.

Fun Gus, with Carl Strang inside

Fun Gus, with Carl Strang inside

The character was created by Andy Kimmel, then a public information specialist for the Forest Preserve District of DuPage County, now an executive with the Forest Preserve District of Lake County (Illinois). Gus’ original home was the Halloween program at Fullersburg Woods Forest Preserve. When I became Gus, on a few selected occasions I carried him to other venues. Once I was asked to provide a special presentation as Gus at a regional conference of heritage interpreters. One of the moments in that hour was a song I wrote for the event, “Fun Gus’ Song.” Here it is, followed by the lyrics.

Fun Gus’ Song

Copyright ©1997 Carl A. Strang

I am a fungus, my mycelium grows

Through fallen leaves and rotting wood.

Then all at once, a new mushroom shows

Where nothing had before stood.

I might be food, or I might cause you to die.

I might decay your rotting bones.

I might help trees to grow to the sky,

A foxfire light might have shown.

And do you see me just as I am?

Or do you see some evil, some good?

A mirror for your own shadow stands

In every toadstool in the woods.

I am a fungus, my mycelium grows

Through fallen leaves and rotting wood.

Then all at once, a new mushroom shows

Where nothing had before stood.

I am a fungus, my mycelium grows.

I send out spores into the sky.

Where they all land, there is none can know.

In faith no reason to try.

This is the rare, serious side of Fun Gus. In the song he refers to fungal roles as decomposers, mycorrhizal mutualists, poisons, foods, and phosphorescent mycelia, while suggesting there may be some metaphoric value in toadstools.

Can you see me just as I am?

Can you see me just as I am?

A mirror for your own shadow stands in every toadstool in the woods.

Small Mysteries

by Carl Strang

Even when distracted the mind notices, finds questions.

Some remain intractable. Why has Culver, Indiana, become turkey vulture central?

Vultures roosting at the Culver town park on a morning last week.

Vultures roosting at the Culver town park on a morning last week.

There have been times in the past decade when 30 or more vultures circled above that part of the town.

Other mysteries are more easily resolved. Back at Mayslake Forest Preserve this week, I noticed a polyphemus moth cocoon on a small tree.

The oval shape, pale color, and loose attachment to a twig are distinctive.

The oval shape, pale color, and loose attachment to a twig are distinctive.

There has been no sign of this large species on the preserve in the years I have been there. But this tree was planted just last year, and checking my notes I found that it was installed in November. Obviously the cocoon had formed in the nursery.

On another day I was startled to see a red cedar decked out in structures like Christmas tree ornaments.

These are the spore-producing structures of the cedar-apple rust, which cycles between the cedars and apples or crab trees, and can impair both host species.

These are the spore-producing structures of the cedar-apple rust, which cycles between the cedars and apples or crab trees, and can impair both host species.

It seems the cool, wet weather promoted the rust’s development on that tree.

A questioning attitude becomes reflexive when one practices inquiry and spends time out-of-doors.

Literature Review: Fungal Evolution

by Carl Strang

Fungi work behind the scenes for the most part, but they have played, and continue to play, essential roles in Earth’s ecosystems. That important work began a long time ago.

We most often notice fungi at the brief times when they grow spore-dispersing structures.

We most often notice fungi at the brief times when they grow spore-dispersing structures.

Floudas, Dimitrios, et al. 2012. The Paleozoic origin of enzymatic lignin decomposition reconstructed from 31 fungal genomes. Science 336:1715-1719.

Comparative genomic and molecular clock analyses in fungi “suggest that the origin of lignin degradation might have coincided with the sharp decrease in the rate of organic carbon burial around the end of the Carboniferous Period.” In other words, the immense volumes of Paleozoic coal accumulated because fungi had not yet evolved the ability to decompose wood down into its nutritious chemical components. After they did so, much less wood survived to become coal.

Wolfe BE, Tulloss RE, Pringle A (2012) The Irreversible Loss of a Decomposition Pathway Marks the Single Origin of an Ectomycorrhizal Symbiosis. PLoS ONE 7(7): e39597. doi:10.1371/journal.pone.0039597

They looked at the genetics of nutrition in Amanita fungi, and found that their mutualistic partnerships with vascular plants are obligate. The fungi have lost two genes that once allowed them to decompose organic matter in the soil, so that they now depend upon their mutualistic partners for carbon. This study refers to another very important ecological role many fungi play. They form partnerships with many green plants, channeling in soil minerals in exchange for other goodies. As the authors point out, this trade no longer is an option: the partners can’t survive without it.

Miscellaneous Encounters

by Carl Strang

It’s time to shake more photos out of the bag, as we are well into the seasonal transition. Back when the weather was hot, a male blue dasher posed at St. James Farm.

For some reason I hadn’t previously been successful in getting a good photo of a male. The forward-cocked wings are a characteristic of the genus.

A few weeks ago some odd looking mushrooms came up beneath a cluster of conifers at Mayslake.

I recognized these from my years in Pennsylvania: old man of the woods. The peculiar flaked surfaces of cap and stem are distinctive.

Recently I shared a photo of a greenstriped grasshopper nymph. At the time, I wondered whether the brown colors of males and the green colors of females might appear as early as the nymph stage. The earlier individual was brown.

Last week I ran across this green one.

So both colors at least are present in the fall. Though I cannot say for sure, the simplest explanation is that the gender-specific colors appear this early in development.

Also last week, a young house centipede explored my office walls.

I marvel at their ability to control all those long legs on a smooth vertical surface.

Of course, one advantage is that the many feet provide lots of little grippers.

Literature Review: Food Web Elaborations

by Carl Strang

Last week I posted an overview of recent research that casts light on food web and ecosystem function. Things are much more complicated than that relatively simple summary when one digs into the details. This week I want to provide a couple disparate examples. Toward the end of the overview I cited some results suggesting that ecosystems with fewer species tend to be less stable, and that such ecosystems often are marginal, for instance because of low productivity. Evolution is a creative force, however, that produces adaptations allowing organisms to persist in such marginal ecosystems. This increases diversity, improving the chance that the associated food webs will persist.

One example pertains to birds (Jetz, Walter, Dustin R. Rubenstein. Environmental Uncertainty and the Global Biogeography of Cooperative Breeding in Birds. Current Biology, 2010; DOI: 10.1016/j.cub.2010.11.075 ). They reviewed the world’s bird species and found that cooperative breeding patterns such as helpers at the nest and other communal reproductive behaviors are more common in places with inconsistent climate patterns, particularly in rainfall.

One illustrative example is the grey-crowned babbler.

The grey-crowned babbler is on the short list of my favorite Australian birds. They often forage in groups, they have amazing silly sounding vocalizations, and they nest communally.

This babbler nest is huge, perhaps 3 feet long.

The cooperative breeding trait allows this species to persist in a difficult desert environment. It’s not the only strategy, as there are plenty of birds in that community which do not nest communally, but again, evolution is a creative force that can find many solutions to survival problems.

Another evolutionary force, leading to stability in a class of mutualistic relationships, was highlighted in a study last year (Kiers, E. Toby, et al. 2011. Reciprocal rewards stabilize cooperation in the mycorrhizal symbiosis. Science 333:880-882). This research looked at mycorrhizae, partnerships in which fungi channel nutrients from the soil into plant roots, and roots provide a medium (sloughing off bark, for instance) in which the fungi can grow.

Many mushrooms are the spore-producing structures of mycorrhizal fungi.

In laboratory experiments Kiers and company found “that plants can detect, discriminate, and reward the best fungal partners with more carbohydrates. In turn, their fungal partners enforce cooperation by increasing nutrient transfer only to those roots providing more carbohydrates…we conclude that, unlike many other mutualisms, the symbiont cannot be ‘enslaved.’ Rather, the mutualism is evolutionarily stable because control is bidirectional, and partners offering the best rate of exchange are rewarded.”

Prehistoric Life 14

by Carl Strang

This year’s winter series is a review of the prehistoric life and geologic history of northeast Illinois. Each chapter will summarize current understanding, gleaned from the literature, of what was going on with life on Earth in a particular span of time, what we know about the local landscape, and what we can say about local life. I include some references, particularly to papers published in the journal Science which commonly is available at public libraries. Contact me if you need sources for other items. The Earth is so old that every imaginable environment was here at some point, from ocean depths to mountaintops, from equatorial tropics to tundra, and from wetlands to desert.

Cenozoic Era, Paleogene Period (65-23.3 million years ago), Paleocene Epoch (65-56.5 mybp)

The Cenozoic Era was named (1841) for the fossil life that characterized it, literally translated “recent life.” Formerly it was divided into two periods, the Tertiary and Quaternary, which no longer are recognized. In recent years it officially has been divided into two different periods, the Paleogene and the Neogene. A proposal under consideration would subdivide the Neogene, reinstating a Quaternary Period that would contain the most recent Pleistocene and Holocene Epochs. The Paleogene Period, established in 1866, defines a time when only a small portion of its fossil species or their very close relatives still are in existence today. It is subdivided into epochs, the first of which is today’s focus. The Paleocene Epoch, first defined in 1874, literally means “ancient recent.” Following Lyell’s original scheme of dividing the Cenozoic Era’s time according to percentage of marine fossil mollusk species still living, the Paleocene has none still living today.

Life on Earth. In New Zealand, researchers have found a heavy layer of fungal spores representing the first few years after the “Chixculub impact” that ended the Mesozoic Era and began the Paleocene (see below). Such abundant fungi performed the decomposition that followed a “wholesale dieback of photosynthetic vegetation” (and this was halfway around the world from the impact site). The fungi were followed by a burst of ferns, a delay then until conifers got going, then a greater delay to the recovered dominance of flowering plants (Science 303:1489). The largest vertebrate to survive the Cretaceous was the freshwater fish-eating reptile Champsosaurus, which survived to the Eocene in North America and Europe.

Imagine a world covered in fungi. That is the image we have of the Earth during the months to years immediately following the impact of the asteroid that marked the beginning of the Paleocene Period. Surviving animals had to be small sized and capable of living on fungi, seeds, or other small animals.

Plant diversity and insect diversity generally were much lower in the Paleocene than in the late Cretaceous, with interesting exceptions that indicate millions of years were needed to re-establish equilibrium in communities of plants and the insects eating them. For instance, in southeastern Montana a high diversity of plant-eating insects occurred on a low-diversity plant community, while another community in Colorado had high plant diversity but low insect diversity (Science 313:1112).

The warmth of the late Paleocene allowed narrow-snouted crocodilians to live in North America and Europe as far north as New Jersey.

The Cenozoic was the time when mammals came to dominate terrestrial animal life on Earth, with the greatest rate of evolution of new families and genera occurring in the early Paleocene. Australia became isolated in the Paleocene, cutting off the flow of marsupials from Antarctica and South America and setting the stage for the most significant marsupial fauna on Earth to evolve from then until recent times. However, North America remained connected to both Asia and Europe through the Paleocene.

Today’s marsupial-dominated Australian fauna, including this wombat, continue a legacy established in the Paleocene.

Paleocene mammals included the multituberculates, a primitive group now extinct, that had been the dominant Cretaceous mammal group. They reached their diversity peak in the Paleocene.

Early carnivore-like mammals, the creodonts (now extinct), appeared in the Paleocene of North America and Europe (with the departure of the dinosaurs, there was an open niche for predators of terrestrial vertebrates as the Paleocene began). True carnivores also emerged in the Paleocene, but the Carnivora of the Paleocene and early Eocene were relatively small and generalized predators, comparable to martens. Thus the creodonts were the significant predatory mammals of these times, rising to prominence in the late Paleocene. 

Another important Paleocene mammal group were the condylarths, a somewhat artificial order that gave rise to the ungulates and whales. The earliest condylarths were rat-sized, but they diversified and ultimately included enormous species. Most were generalized in diet, though some tended more toward herbivory and others were more carnivorous.

Treeshrews arose in the early Paleocene (Science 318:792). In the late Paleocene, new groups that appeared were order Perissodactyla (including horses in North America), bats (early bats were flying before they developed the echolocation ability: Science 318:1237), Edentata (in S. America), and rodents (in N. America). Unusually well preserved skulls of a species in the extinct family Apatemyidae reported in 2010 tie the primates to the rodents, treeshrews and flying lemurs.

Fossil bird, Field Museum collection. Modern birds came into their own in the Paleocene.

Out of the great diversity of early bird groups, only one (Neornithes, the modern birds) survived past the end of the Cretaceous. The modern orders of birds diverged during the Paleocene.

Local landscape. Our area may have been directly affected by the meteorite that struck the Yucatan area to end the Mesozoic era. There is evidence that the meteorite came in at a shallow angle from the south, and so scattered debris into North America. Our continent’s forests were flattened except in the far north and in refugia where mountains provided protection from the blast. A tsunami would have been funneled straight into the mid-American sea, and conceivably could have reached Illinois. After the time when photosynthetic vegetation was largely or entirely killed off, as mentioned above, much of the continent may have been “little more than a field of ferns” for up to thousands of years (Science 294: 1668-9) as surviving spores and seeds in the soil re-established terrestrial vegetation. Incidentally, astronomers are 90% certain that the source of the Cretaceous-ending meteorite was a collision between asteroids beyond Mars nearly 100 million years earlier (Science 317:1310).

Our area remained dry land throughout the Cenozoic, though the sea touched the southern tip of Illinois in the Paleocene and Eocene (leaving the nearest deposits for those epochs to here). The climate was warm, moist and tropical with little seasonality in the Paleocene. Tropical forests developed here after the recovery from the meteorite damage.

Local life. At our latitude in the Paleocene there were diverse ferns, ginkgoes, araucarias, palms, members of the walnut and birch families, dogwoods, chestnuts, oaks, sycamores, hackberries, elms, spicebush, sassafras, magnolias, and members of the grape family. Our forest would have been tropical, and evergreen or seasonally deciduous at different points in the Paleocene.

Later in the Paleocene, creodonts were likely here. The first large local mammalian predator was likely a cat-like creodont in the genus Oxyaena. Other creodonts showed adaptations for scavenging. Hyaenodontids were creodonts adapted for running, like dogs or hyenas.

There was an early North American group of primitive mammals, the Taeniodonta, resembling ground sloths but not related to them, that lasted from the early Paleocene to the late Eocene (widely distributed, but always rare; the genus Ectoganus probably was represented locally by a species in the 100-200-pound range).

Most known species of the diverse “order” of condylarths were North American. They were mainly omnivorous, though the most primitive one, Protoungulatum from the early Paleocene of North America and Europe, was more of a specialized predator. The majority, however, were ecologically more like raccoons or bears. Others were more on the vegetarian end of the scale, like pigs and peccaries. The widespread, sheep-sized Phenacodus, late Paleocene to middle Eocene, and its relatives are a good candidate as the ancestors of the Perissodactyla (odd-toed ungulates such as horses). Ungulates in the order Mesonychia tended to predatory habits, and among them were the largest mammals of the early Paleocene (10x the usual rat size). Later, still larger members of this group shared predatory dominance with the creodonts. Coyote-sized Dissacus occurred all over the northern hemisphere.

In the late Paleocene and early Eocene our area may have had a species of Coryphodon, a genus ranging through Europe, Asia and North America, possibly a swamp dweller with a generalist diet. These were members of the Paleocene-Eocene order Pantodonta, among the earliest post-Cretaceous mammals to attain large size. Species ranged from tapir- to ox-sized.

Multituberculates were important in nearly all Paleocene faunas in North America. They ranged from small mouse to beaver in size. An example is Ptilodus, a squirrel-like tree-dweller that probably was an omnivore (I think here of the scrat, the acorn-obsessed critter in the Ice Age animated films). Another North American multituberculate, Taeniolabis, was beaver sized and (unusual for the time) a specialized herbivore.

Early arboreal mammals in North America were primates or primate relatives similar to today’s treeshrews. A late-Paleocene genus, Plesiadapis, occurred in both North America and Europe. Another family culminated in the genus Carpolestes, possessing the only fingernails (as opposed to claws) known outside the true primates. Two families were lemur-like.

The fish-eating Champsosaurus, mentioned above, may have inhabited local rivers. There would have been a variety of birds, locally, too.

Prehistoric Life 9

by Carl Strang

This year’s winter series is a review of the prehistoric life and geologic history of northeast Illinois. Each chapter will summarize current understanding, gleaned from the literature, of what was going on with life on Earth in a particular span of time, what we know about the local landscape, and what we can say about local life. I include some references, particularly to papers published in the journal Science which commonly is available at public libraries. Contact me if you need sources for other items. The Earth is so old that every imaginable environment was here at some point, from ocean depths to mountaintops, from equatorial tropics to tundra, and from wetlands to desert.

Pennsylvanian Period (320-286 million years ago)

The Pennsylvanian Period is named for the state of Pennsylvania (1891). This North American subdivision of the European Carboniferous Period is distinguished by many cyclic repeated advances and retreats of the sea, as indicated by alternating rock layers.

Life on Earth. This was the time of the coal forests, when the growing land area provided the home for forests of lycopsids (club mosses, the most abundant trees), sphenopsids (the group containing today’s scouring rush, horsetails and other members of genus Equisetum), ferns (including tree ferns), and seed ferns. There were early conifers as well. These were vascular but not flowering plants. Most coal was produced during this period because fungi, critical to decomposition, had not yet developed that ability to a significant extent. Dead plant tissue piled up without breaking down, ultimately was buried and fossilized into coal. As a result, oxygen built in the atmosphere to an all time high of 30% (Science 316:557).

You can see a life-sized reconstruction of a Pennsylvanian forest at the Field Museum in Chicago. Here are some model sphenopsids.

The earliest Amniota (the terrestrial egg-bearing group ultimately including reptiles, birds and mammals) appeared and diverged in the Pennsylvanian, producing the cotylosaurs (and other anapsid reptiles, a group represented by turtles and tortoises today; fossil cotylosaurs have been found as close to Illinois as Nova Scotia), synapsids (also known from N.S. and the group from which mammals ultimately evolved; the basal synapsids are referred to as pelycosaurs), and the diapsids, a reptile group that evolved into lizards, snakes, dinosaurs, birds and crocodiles.

Winged insects (including the first mayflies and enormous primitive dragonflies) first appeared in the Pennsylvanian, as did cockroaches, grasshoppers and crickets. The earliest beetle was reported from Illinois fossil material in 2009 (J. Paleont. 83:931). Some invertebrates, such as the dragonflies and certain millipedes, reached giant sizes (thanks at least in part to the elevated oxygen levels).

Local landscape. In Illinois, the sea continued its advance and retreat cycling, so that our area alternated between marine and land, often low and swampy. Our area remained just south of the equator, and the climate was warm and humid.  It is thought that alternating periods of glaciers forming and thawing on the southern Gondwana supercontinent (at that time drifting over the South Pole) caused the rises and falls of sea level that produced the local advances and retreats of the sea. Over geologic time, glacial episodes typically are associated with a continental mass at one of the poles (Antarctica in recent times).

Tree ferns still exist today. This one in Tasmania had a thick stem more than 10 feet tall.

The North American continent was beginning to collide with Europe and Africa as the sea that had begun to appear between them closed, forming the northern supercontinent of Laurasia. This event is what lifted our part of the world above the sea for good.

The nearest Pennsylvanian bedrock to Chicago is the Mazon Creek area (much of Illinois’ bedrock is Pennsylvanian), except for some bits in the Des Plaines Disturbance.

Local life. Coal forests dominated Illinois during the Pennsylvanian. Not only was coal left (itself fossil plant material), but remains of a variety of plant and animal fossils can be found just a little south of us in the world-famous Mazon Creek deposits of Middle Pennsylvanian age, just a little southwest of Joliet. Seed-fern leaves such as Medullosa, Neuropteris inflata, N. scheuchzeri, N. ovata and N. rarinerus are especially abundant (note: names of these plants are confusing, because different names are given to different parts such as leaves, stems and reproductive parts). There also were the giant sphenopsid Calamites, the smaller weedy horsetail Sphenophyllum, the tree fern Psaronius, small ferns (Pecopteris, Sphenopteris, Alloiopteris), the conifer relative Cordaites, giant club moss relatives Cyperites, Lepidodendron, Lepidophloios, and Sigillaria (up to 6 feet in diameter!), and other, smaller club mosses (Lycopodites, Bothrodendron).

Here are some giant club mosses in the Field Museum exhibit.

Most bizarre among the diverse aquatic animals was the Tully monster (Tullimonstrum gregarium), first found by amateur fossil collector Francis Tully, Illinois’ state fossil, and only known from this area. There were horseshoe crabs (Palaeolimulus, Euproops), freshwater fish (Rhabdoderma oxiguum, Conchopoma edesi, Elonichthyes peltigerus, Platysomus circularis), and mollusks, as well as a lamprey-like fish, Actinopterygian fishes (Elonichthys pettigerus, Platysomus circularis), polychaete worms (Astreptoscolex anasillosus, Escorites zelus, and others), shrimps (Belotelson sp., Kallidecthes richardsoni, Acanthotelson stimsoni, and others), a sea cucumber (Achistrum sp.), a nematode (Nemavermes mackeei), a chiton (Glaphurochiton concinnus), ribbon or priapulid worms (Archisymplectes rhothon, Priapulites konecniorum), the arrow worm Paucijaculum samamithion, the spoonworm (phylum Echiura) Coprinoscolex ellogimus, jellyfish (Essexella asherae, Octomedusa pieckorum, Anthracomedusa turnbullii), cephalopods, brachiopods (Lingula sp.), the scallop Aviculopectin mazonensis, as well as several “mystery animals” of unknown affinities. 

The Field Museum model forest includes a millipede you could put a saddle on!

Land animals included centipedes, millipedes (the giant millipede Arthropleura cristata was a flat species, 16” wide and more than 6 feet long), scorpions, cockroaches (Platymylacris paucineruis) and their relatives (Gerarus danielsi, G. vetus), and spider-like arachnids. There were amphibians (Amphibamus grandiceps, A. yelli).

The upland trees, less well known, were different from those in the swamps, and included the genera Megalopteris and Lesleya. An upland animal was the scorpion Labriscorpio alliedensis.

Prehistoric Life 6

by Carl Strang

This year’s winter series is a review of the prehistoric life and geologic history of northeast Illinois. Each chapter will summarize current understanding, gleaned from the literature, of what was going on with life on Earth in a particular span of time, what we know about the local landscape, and what we can say about local life. I include some references, particularly to papers published in the journal Science which commonly is available at public libraries. Contact me if you need sources for other items. The Earth is so old that every imaginable environment was here at some point, from ocean depths to mountaintops, from equatorial tropics to tundra, and from wetlands to desert.

Silurian Period (438-408 million years ago)

The Silurian Period was named for the Silures (1835), another ancient Welsh tribe. Its fossils were recognized as distinct from those of the preceding Ordovician and following Devonian periods. Its beginning formally is defined by the first appearance of the graptolite species Akidograptus ascensus.

Life on Earth. During the Silurian, the Earth generally showed a warming trend after the ice age that ended the Ordovician. The Silurian reefs, which continued to be based mainly on stromatoporoids and tabulates, were huge. Brachiopods and bryozoans (including a number of colonial, massive stony or sea-fan-like forms) dominated the species count, but corals and echinoderms increased in importance. Nautiloid cephalopods and graptolites largely disappeared by the beginning of the Silurian. Eurypterids (sea scorpions, a group of chelicerate arthropods) appeared in the Silurian, some reaching 10 feet long. Jawless, armored fishes (Agnatha) became more diverse.

A significant step was the appearance of the first vertebrate jaw by the late Silurian, developed from gill arches in the first placoderm fishes and early sharks.  Diversifying early land plants were joined by the first fungi. The first terrestrial chelicerate arthropods (scorpions and eurypterids) had appeared by the end of the Silurian. These were very similar to marine forms of both groups. For instance, Brontoscorpio was an earlier Silurian marine scorpion, very similar to the familiar scorpion shape, which reached 3 feet in length. Genetic studies tie insect origins to crustaceans like today’s fairy shrimp and water fleas, the split occurring near the end of the Silurian. Also, millipedes and centipedes (which evolved in the Devonian) appear to be connected to chelicerate arthropods.

One place where the Niagaran formation is at the surface is at the tip of the Bruce Peninsula in southern Lake Huron.

Local landscape. Our area was a shallow, clear, saltwater sea with abundant dome-shaped reefs. The reefs were part of a barrier reef system surrounding the Michigan Basin. The rock is composed of dolomite, which is a limestone (calcium carbonate) in which magnesium replaces part of the calcium, the replacement possibly having occurred after the limestone was deposited. DuPage County’s bedrock thus is a part of the Silurian layer called the Niagaran formation, which forms a bedrock ring including the western shore of Lake Michigan, the Door peninsula, the southern shore of the U.P., the islands dividing Lake Huron from Georgian Bay, and a zone connecting to Niagara Falls, with large areas curving through Indiana and parts of Ohio. Outliers can be found in eastern Iowa. Our area probably was between the equator and 20° south latitude. The big Thornton Quarry on either side of Interstate 80-294 is mining one of the larger known reefs in this formation.

This structure, referred to as a “flowerpot,” is an isolated pillar of the Niagaran dolomite. It is on an island just off the tip of the Bruce Peninsula.

Local life. Fossils of the Niagaran formation found locally include reef-forming corals (including antler forms and large lumps such as Cladopora reticulata, Halysites catenularia and Favosites niagarensis). Other attached forms include rugose (horn) corals (Asthenophyllum racinensis, Dalmanophyllum wisconsinensis, Pycnostylus guelphensis); bryozoans (Fenestrellina spp., Hallopora ellengantula, Pachydicta crassa); calcareous algae (e.g., the plum-shaped green lump Calathium egerodae); and stromatoporids. Chert nodules are thought to have been derived from the hard parts of sponges (great for arrowheads, lousy for stone crushing machines), but at least one identifiable fossil sponge is known, Calathium sp. The diverse brachiopods include Eospirifer(Spirifer) radiatus, Apopentamerus racinensis, Leptotaena (Leptaena)  rhomboidelis, Rhynchotreta cuneata, Atrypa reticularis niagarensis, Schucheretella subplana, Uncinulus stricklandi, Meristina maria, Conchidium laqueatum, Kikidium, and Wilsonella. There also are several species of crinoids (Crotalocrinites cora, Lampterocrinus infatus, Marsupiocrinus chicagoensis, Siphanocrinus nobilus, Eucalyptocrinus crassus, Periechocrinus infelix), and crinoid-like cystoid echinoderms (Caryocrinites ornatus, Holocystites alternatus)

This diorama is part of the Evolving Planet exhibit at the Field Museum of Natural History. It portrays a Silurian reef.

Mobile life forms include trilobites (Bumastus niagarensis, B. harrisi, B. insignis, Calymene celebra, C. niagarensis, Arctinurus chicagoensis, Dalmanites sp., [=?] Dalmanella platycordata), and mollusks (snails Euomphalopterus halei, Tremanotus alphaeus, T. chicagoensis, Straparollus magnus, Lophospira rotunda, Phanerotrema occidens; pelecypods Mytilarca denticostia, Matheria recta; straight-shelled cephalopods Amphicyrtoceras orcas, Dawsonoceras bridgeportensis, Kionoceras orus, K. cancellatum; and at least one coil-shelled species, Discoceras marshi).

This fossil trilobite is in one of the Silurian dolomite flagstones at Fullersburg Woods, mined from the Lemont Quarry and used by the Civilian Conservation Corps in its construction projects at that forest preserve.

The earlier Alexandrian series, also dolomite, has the brachiopods Platymerella manniensis, Microcardinalia pyriformis, and Pentamerus oblongus.

Vertebrates, i.e., fishes, continued to be relatively uncommon through at least most of the Silurian, and apparently fossils of them have not been found locally.

Happy New Things

by Carl Strang

However familiar a landscape has become, there always is something new to discover in it. I have begun my second year at Mayslake Forest Preserve, and still I am finding rather large organisms I completely missed last year. Recently I noticed a conspicuously flowering shrub I did not see in 2009.

Unless I miss my guess, this is a blackhaw, one of the native viburnums. Fungi are an entire group with which I have only spotty, passing familiarity. Here is one of the common ones, Polyporus squamosus, which appears on the trunks of several different tree species in spring.

The scaly looking shelves of these reproductive structures are worth taking some time to enjoy. Novelty and surprise certainly are among the factors that draw me again and again into wild places, even ones with which I am reasonably familiar.

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