Digging Holes

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Painted Desert of Petrified Forest National Park in Arizona.  The distant skies are filled with virgas, rain that evaporates before it reaches the ground.  Image credit: Curious Sengi.

This post is part of a series commemorating the 150th anniversary of the Yale Peabody Museum of Natural History.  You can read about the first specimen to enter the Vertebrate Paleontology collection here.  This story is about the most recent fossils to enter the collections — specimens that were collected just over a month ago in May and June 2016 during a field expedition to the Triassic rocks of Petrified Forest National Park, Arizona.   

Our dig site is marked by a dark blue tarp, a faint pinprick of artificial color in the Painted Desert.  At this point, we had already trudged over a mile through the trackless desert:  picking our way between the low scrub, avoiding rattlesnakes, and using a distant red-lipped hill as our only bearing.  Now we stood at the edge of badlands, where the fossils are.  The heat of the day is rising.  And that blue tarp is still painfully far away.

No sane human being would be out here.

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The black arrow marks the location of the blue tarp that covers one of the multiple dig sites worked during the 2016 field expedition.  Image credit: Curious Sengi.

In our heat-addled hallucinations, we see the dreamscape of the desert, where gypsum erupts from the red earth like misshapen white molars or glittering panes of broken glass.  Millions of years of sediment deposition stand out in vivid colors, much too reminiscent of seven-layer dip and Neapolitan ice cream — trivial pleasures in an endless panorama.  Fat horny toads blink their stoic welcome.  Small lizards eye us suspiciously and make their challenge with jerky little push-ups before losing their nerve and diving for cover.  Lanky jackrabbits flash across the hills and disappear like omens.  Vampiric winds suck the moisture from our lips.  Dust devils gather.  When it stops, the cedar gnats come.  Bone chips weathering out of a hillside metamorphose into wishful thinking with the changing light.  Black zigzag lines on a pale potsherd is a startling reminder that we were not the first to venture out here.  But we are here now, driven by the hope of finding ancient beasts beyond all imagining.

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Colorful layered sediments. Image credit: Curious Sengi.

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Native American potsherd discovered while hiking. All archaeological artifacts found in the park are photographed, given GPS coordinates, and reported to park officials. The artifacts themselves are left untouched. Image credit: Curious Sengi.

The desert is a ravishing world that simultaneously destroys and restores.  For those moments of absolute beauty and discovery, we gladly welcome all the associated abuses it renders upon us.  After all, we are far away from the annoyances of home and office.  These are the few precious weeks out of every year we have in order to collect.  Collecting fossils is, of course, always a grand adventure of luck, sharp eyes, and digging holes.  But each expedition is just a beginning, the very first unfolding of multiple layers of discovery.

It starts with your eye catching something a little different, something a bit unusual and curious.  Perhaps it is the color or texture or shape — even just a feeling — that draws you to a piece of bone on the ground surface.  Other times, it is stunningly obvious:  a tooth with glossy enamel shining on the surface of rock pulled out from a quarry.  But for the most part, all you can know is that this is a fossil.

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A little spot of homemade shade is a respite from a full day in the sun and wind. Image credit: Curious Sengi.

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Life under the tarp.  Fossil preparator Christina Lutz works on undercutting a plaster jacket. Image credit: Curious Sengi.

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Big bone weathering out the side of a hill. Image credit: Curious Sengi.

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Yale Peabody Museum’s chief fossil preparator, Marilyn Fox, puzzles over the big bone. After brushing away the dirt and layer of bone weathered into dust, some shapes begin to take form.  Even so, the identity of the fossil remains a mystery.  Image credit: Curious Sengi.

Our priority in the field is to bring fossils back safely to the museum.  The care and preservation of specimens begins out there under the sun and blowing dust.  A touch of archival glue might help consolidate fragile pieces together.  Loose specimens are wrapped in packets of toilet paper and aluminum foil.   Larger specimens or bone embedded in the matrix are given a generous buffer of surrounding rock before being encased in hard protective plaster jackets.  Everything is meticulously labelled with field numbers and recorded with good locality data.  Always, good locality data.

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Some of the treasures brought back from the expedition. These plaster field jackets cover and stabilize fossils that remain embedded in rock. Collectors mark approximate areas where bone is located in the block. Image credit: Curious Sengi.

These bundles return to the museum, often with very little idea of what the bone is or what kind of animal it belonged to.  That second moment of discovery comes when the fossils are prepared out of the rock, unveiling the extent of their shape and identity.  It takes skill and patience to prepare fossils, so this moment might be delayed by months or even years.  Even then, careful preparation might only reveal that an unidentifiable bone shard is just an unidentifiable bone shard.  Stunning or not, all of these specimens will eventually be accessioned into museum records and properly housed to ensure their long-term preservation.

The next moments of discovery are potentially infinite.  What can we learn from this specimen?  What does it say about anatomy or ecology or geological processes?  This moment could come from an observation waiting to be made tomorrow.  It could also stretch off into the future as generations of researchers find new questions to ask and innovate better ways of extracting information.  The vertebrate paleontology collections at the Yale Peabody Museum have the benefit of a long history — specimens that were discovered over a century ago have not exhausted their scientific value and are now being investigated using novel technologies, such as microCT scanning, that were beyond the wildest dreams of their original collectors.

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Some dig sites contained bone encrusted in an unknown material similar to oxidized iron. Preparator Christina Lutz is experimenting with chemical methods to remove this layer. Research in museums also includes discovering better ways to prepare, conserve, and preserve specimens. Image credit: Curious Sengi.

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Specimens fresh from the field. Image credit: Curious Sengi.

We have now returned as collectors ourselves.  Even at our desks and computers, we feel a fellowship with all those who experienced the beauty and brutality of the desert in search of fossils.  We also feel a certainty that those long-dead collectors would be as grateful as we are, to know that our contributions will endure in the hands of dedicated museum staff and curious minds yet to arrive.  These specimens will be here, waiting for their many moments of discovery to unfold.

And we also wait here, watching the calendar for the next time we can step out into field.

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The joys of camp. Some of the field crew prepare dinner. Members of our expedition came from all backgrounds and experience levels. The team included undergraduate students, volunteers, museum professionals, and academics. Image credit: Curious Sengi.

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Until next time. . . . . Image credit: Curious Sengi.

Special thanks to Marilyn Fox and Christina Lutz for their help in preparing this post.

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Notes from the Field No. 4: Darwin’s Remedy

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Painting of Botafogo Bay, Rio de Janeiro, Brazil by Augustus Earle (c. 1783 – 1838).  Earle was an artist specializing in exotic scenes captured during his travels.  He was briefly a part of the HMS Beagle crew alongside Darwin.  Image credit: newtonsapple.org.uk.

Charles Darwin (1809 – 1882) landed in Rio de Janeiro in the spring of 1832 during the first year of the HMS Beagle voyage.  Traveling by boat made Darwin horribly seasick, but the tropical jungles were full of potential health dangers — yet another source of anxiety.  Throughout his adult life, Darwin’s health was a complicated flux of chronic symptoms with perhaps even a tendency towards hypochondria.   Despite these difficulties, he still kept his eye on the natural world and recorded his observations.

11 April 1832

Passed through several leagues of forest. very impervious trees not large: I here first began to feel feverish shivering & sickness. much exhausted: could eat nothing at one oclock which was the first time I got anything. — travelled till dark: miserably faint & trouble with faintness.

At night we slept 2 miles S of Marica: felt very ill in the course of day I thought I should have dropt off the horse: horrors of illness in foreign country: during the morning C Frio appearing from refraction like inverted tumblers. Gneiss dipping to the South (& then the north).

12 April 1832

Started in the morning & doubted whether I could proceed. — Cinnamon & port wine cured me

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Life-size figure of a young Darwin on display in Sao Paulo, Brazil.  Honestly, he still looks pretty queasy.  He could also be completely bummed out because upon arriving in Rio de Janeiro, he received letters informing him that his sweetheart married another man just days after Darwin left England.  Image credit: Rodrigo Barbassa via The Dispersal of Darwin.

 

Quotation Source

The Complete Work of Charles Darwin Online: Rio notebook.  John van Wyhe, editor.  2002.  http://darwin-online.org.uk/

 

Notes from the Field No. 2: Erstwhile Pets

Scarritt Pocket

Mammal fossils lured paleontologists to Oligocene age rocks in Patagonia of Chubut Province, Argentina. The deposits pictured here were discovered by G.G. Simpson heading the Scarritt Expedition in 1934.  This photograph comes from a modern paleontological expedition revisting the area.  Image credit: Vucetich et al. 2014. “A New Acaremyid Rodent (Caviomorpha, Octodontoidea) from Scarritt Pocket, Deseadan (Late Oligocene) of Patagonia (Argentina).”  Journal of Vertebrate Paleontology 34 (3): 689 – 698.

In the 1930s, the reknowned American paleontologist George Gaylord Simpson (1902 – 1984) led a number of fossil hunting expeditions with the American Museum of Natural History to Patagonia in the southern end of South America.  Simpson was very much interested in an assemblage of ancient mammals living in “splendid isolation” on the island continent of South America.  His research centered upon these endemic radiations and their eventual fate when a narrow landmass, the Isthmus of Panama, arose at the end of the Pliocene (approximately 3 million years ago) and began the Great American Faunal Interchange.  While searching for evidence from this epic story of South-meets-North, the expedition lightened their days enjoying the antics of local wildlife they adopted as camp pets.

The vast plains of Patagonia are a barren and savage waste in which man seems an interloper.  Here in the far south of South America nature never smiles. . . Yet Patagonia has its own children, living in constant fear and combat, but somehow contriving to flourish and finding in this desolation a home suited to their own wild temperaments. . . .

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Simpson at the dig.  A skeleton is carefully excavated, covered in shellac, and bandaged for safe transport.  Image credit: Simpson 1932.

We caught one of the babies [a Darwin’s Rhea, Rhea pennata] and christened him Charita. . . . [he] soon forgot his brothers and sisters and lived with us contentedly, a silly creature with feet much too big for it, its body the size and shape of the egg from which it came (where the neck and legs fit in I do not see), covered with soft down, dark brown and striped with white like a skunk.  His idea of heaven was to wedge himself tightly between two hot pans beneath the camp stove.  When deprived of his sensuous pleasure, he divided his time between trying to crawl into our pockets and trying to scratch his head, laudable ambitions neither of which was ever wholly achieved. . . . He used to sleep with one of us, and soon became a real member of the family.  His cry was a sad whistle, slurring down the scale and ending with a pathetic tremolo. . . . he would come running whenever we called him and would carry on long conversations with us.

Charita the Rhea Chick

Expedition members tended to name their pets after the local language — in this case, “Charita” referred to “ostrich chicks in general.”  Of course, Charita was not actually an ostrich, but a related ratite indigenous to South America known as a rhea.  Drawing by E.S. Lewis.  Image credit: Simpson 1932.

Our long favorite was a pichi [i.e., armadillo] named Florrie. . . . She came to tolerate us as servitors but never displayed any demonstrative affection.  One can no more pet an armadillo than one can pet an egg or, more aptly, a tortoise, and her own attitude was always one of vapid selfishness.  Yet she fully earned her keep.  As she wallowed in a saucer of condensed milk we laughed more at than with her.  She never learned to lap it up cleanly with her long tongue, but must always get her sharp, flexible snout in it too, so that attempts to breathe resulted in convulsive coughs and mighty blowing of bubbles.  She would start to wander off, then suddenly remember the milk, dash back to it in the most business-like way and start drinking again, only to lose interest, wander off again, and repeat the whole process several times.

There was always something vague about Florrie.  Her thick skin seemed to be an index to her mentality and emotions.  Almost the only real emotion she betrayed was when first captured.  Then, if touched, she would suddenly jump, at the same time emitting a convulsive wheeze, a maneuver as disconcerting as the explosion of a mild cigar.  Later she ceased to bother.  If she wandered off when let out, it was rather from absent-mindedness than from any active dislike for our society.  She seemed to think with her nose, and when thus let out for exercise she would trot busily from bush to bush, poking her nose into the ground beneath and sniffing violently.  Once she got away altogether and for several days we mourned her for lost, when one morning she wandered back into camp with her usual air of preoccupation.  The cook, whose special friend she was, swore that she returned for love of us, and another said she had returned for free meals, but I maintain that she had simply forgotten that the camp was there two minutes after she left it, and stumbled on it again quite by accident in the course of one of her sniffing parties.

Florrie the Armadillo

Drawing by E.S. Lewis.  Image credit: Simpson 1932.

These erstwhile pets shared in the daily life of the expedition.  What, if anything, was planned for their ultimate fate is a bit more ambiguous.  Simpson devotes a great deal of space in this popular account to the culinary merits of the local wildlife (a hallowed tradition in scientific expeditions) and both rheas and armadillos were eaten regularly.  Whether the men planned to abandon the animals, eat them, take them back to New York, or have them prepared as museum specimens, that decision soon became moot.  For “. . . .Charita met an untimely end.  He developed an unwholesome appetite for kerosene and, one day, finding a whole pan of this delightful beverage unguarded, he overindulged.  All afternoon, he wandered about vaguely as if something was very much on his mind, or stomach, and next morning he was dead.”  Likewise, Florrie, who was a cheerful presence in camp for several months, ended up being accidentally crushed to death.  Despite these unhappy ends, it is clear that the hapless bumblings of animals like Charita and Florrie were the focus of much entertainment and affection during the long months of isolation grueling in the field.  

Quotation Source

Simpson, George Gaylord.  1932.  “Children of Patagonia.”  Natural History 32 (2):  135 – 147.

Notes from the Field No. 1: Darwin v. Octopus

Charles Darwin had all the anxieties typical of a recent college graduate:  uncertain of what was to come, depressed by the prospects available in the Real World.  He had already disappointed his physician father once by dropping out of medical school, so he studied theology at Cambridge in order to take up the gentlemanly profession of being a parson.  But young Charles was clearly procrastinating and desperately planning one last hurrah of the naturalist’s life.  Then one late summer’s day, he opened a letter offering him an opportunity to sail around the world aboard the HMS Beagle. . . . 

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The first port-of-call in what would become a five year voyage around the world.  The Beagle landed at St. Jago, Cape Verde Islands off the coast of West Africa.  It was Darwin’s first real intoxicating taste of the tropics.  Image credit: Barrow, John. 1806. “A Voyage to Cochin China, in the years 1792, and 1793.” via The British Library (Flickr)

28 January 1832, St. Jago

Found amongst the rocks West of Quail Island at low water an Octopus.— When first discovered he was in a hole & it was difficult to perceive what it was.— As soon as I drove him from his den he shot with great rapidity across the pool of water.— leaving in his train a large quantity of the ink.— even then when in shallow place it was difficult to catch him, for he twisted his body with great ease between the stones & by his suckers stuck very fast to them.— When in the water the animal was of a brownish purple, but immediately when on the beach the colour changed to a yellowish green.— When I had the animal in a basin of salt water on board this fact was explained by its having the Chamælion like power of changing the colour of its body.— The general colour of animal was French grey with numerous spots of bright yellow. . . . Over the whole body there were continually passing clouds, varying in colour from a “hyacinth red” to a “Chesnut brown”.— As seen under a lens these clouds consisted of minute points apparently injected with a coloured fluid. The whole animal presented a most extraordinary mottled appearance, & much surprised very body who saw it. . . . The animal seemed susceptible to small shocks of galvanism: contracting itself & the parts between the point of contact of wires, became almost black.— this in a lesser degree followed from scratching the animal with a needle.— The cups were in double rows on the arms & coloured reddish.— The eye could be entirely closed by a circular eyelid.— the pupil was of a dark blue.— The animal was slightly phosphorescent at night.

The common octopus, Octopus vulgaris. Image credit: Jatta, Giuseppe.  1896.  “Cefalopodi viventi nel Golfo di Napoli (sistematica).” Fauna und Flora des Golfes von Neapel und der angrenzenden Meers 23 via Biodiversity Heritage Library (Flickr).

30 January 1832, St. Jago

Found another. changed its colour in the same manner when first taken. Caught another: I first discovered him by his spouting water into my face when I certainly was 2 feet above him. When seen in water was of dark colour with rings: being with difficulty removed from a deep hole & placed in a puddle of water swam well & emitted a dark Chesnut brown ink.— he continued likewise to spout water, evidently being able to direct his siphon.— When on land did not walk well having difficulty in carrying its head which it continued filling with air as before with water.— From same cause the animal often made a noise when squirting out water. They are so strong & slippery that one hand is insufficient to hold them.— Whilst swimming generally changed colour & seemed to imitate colour of the rocks.—

Chromatophore

Image credit: Cloney & Florey 1968.

 

Darwin was obviously mesmerized by the way the octopus changed its colors like “passing clouds” and he noted the “minute points apparently injected with a coloured fluid.”  What he saw were chromatophores, specialized cephalopod pigment cells.  Each chromatophore is individually innervated (labeled “Axon” in lower left of the diagram) and equipped with radial muscle fibers that pull the chromatophore from a dense ball of dark pigment into a flat, splayed out pigment field that blossoms with color.  

References

Cloney, Richard A. & E. Florey.  1968.  “Ultrastructure of Cephalopod Chromatophore Organs.”  Zeitschrift für Zellforschung 98:  250 – 280.

The Complete Work of Charles Darwin Online.  John van Wyhe, ed.  2002.  http://darwin-online.org.uk/

Desmond, Adrian & J. Moore.  1991.  Darwin:  The Life of a Tormented Evolutionist.  W.W. Norton & Company.