Wednesday, October 30, 2013

Coming Out of Left Field, A Snail Takes a Wrong Turn

The Oxford American Dictionary offers two figurative definitions for left field:  (1) "a position or direction that is surprising or unconventional;" (2) "a position of ignorance, error, or confusion."
A wonderfully funny explanation for the expression that something or someone “came out of left field” or “was out in left field” is premised on the “fact” that roughly a century ago the Chicago Cubs played in the West Side Grounds which had a left field abutting the University of Illinois’ Neuropsychiatric Institute.  So, what came out of, or was in, left field might well have been out of touch, indeed, maybe crazy.  Sadly, that explanation is too good to be true.  Yes, the Cubs played there from 1893 to 1915, but that was well before 1939 when the Neuropsychiatric Institute was built on what had been the West Side Grounds’ left field.  (Rosemarie Ostler, Let's Talk Turkey:  The Stories Behind America's Favorite Expressions, 2008, p. 163.)

One of the better possibilities for the expression's origin rooted in baseball is that many early major league baseball stadiums were decidedly asymmetrical and, apparently, left field was often the deepest part of the ballpark.  So, the left fielder was literally way out in left field (away from the action of the game) and any time he threw a ball back toward the infield, it came from way out of left field.

What came out of left field this past week (via a friend) fit the first Oxford American Dictionary's figurative definition - a surprise (though eventually it led to the second definition).  It was a fossil marine snail shell found on the coastline near the town of Walton-on-the-Naze, in Essex County, England.  This is a Neptunea contraria (Linnaeus, 1771) and dates from late in the Pliocene Epoch (3.6 to 2.6 million years ago).

(Though there’s some debate about the name of the species, I'm sticking with N. contraria as have better and more expert thinkers than I.)

I certainly wasn’t expecting to receive this shell.  What was intended to be the real hook for me about this specimen was that it was still filled with matrix from where it was found, offering an irresistible opportunity to discover microfossils tucked into its curved chambers.  But, frankly, though I’ve begun the exploration of the microfossils (more on that in a later post), I’ve been captured by so much else about this particular fossil that I had to write about that.  Yes, all that came out of left field.

The location where the fossil was found – Walton-on-the-Naze – is a small town located on England’s east coast, on the shores of the North Sea.  The melding of name and location strikes me as quintessentially British.


The Oxford English Dictionary defines naze as:  “A promontory, a headland, a ness.”  The OED observes that its origins are uncertain, though it suggests it may have Scandinavian roots.  Bill Griffiths, in Fishing and Folk:  Life and Dialect on the North Sea Coast (2010, p. 10), speculates that it may derive from the French nez meaning nose.

A view of the area around Walton-on-the-Naze from Google Earth clearly shows the naze, which is the headland, to the northeast of the town, jutting into the North Sea.  Sort of nose-like.

The eroding cliffs from which the fossil came follow that coastline to the northeast.  The London Clay Formation, laid down in the Eocene Epoch (56 to 34 million years ago), forms the base of the cliffs.  That formation is overlain by the Red Crag Formation which is nearly 50 million years younger; this unconformity is the product of marine erosion washing away millions of years of intervening deposits.  The Red Crag Formation, source of this fossil, dates from the late Pliocene Epoch (3.6 to 2.6 million years ago).

Red?  Crag?

Geologist Gerald Lucy explains both in Essex Rock:  A Look Beneath the Essex Landscape (Essex Rock and Mineral Society, 1999).  Let’s take the latter one first.
The word “crag” was formerly a local term used in East Anglia to describe fine gravel and sand but geologists have now adopted it to designate some of the characteristic marine deposits of Pliocene and Pleistocene age in Essex, Suffolk and Norfolk.  (p. 53)
The coloring (more orangey than red to my eye) is, according to Lucy, the result of a several step reaction:  pyrite (iron sulfide) washed out of the underlying London Clay, the iron in the pyrite oxidized into rust-colored iron oxide which, in turn, stained the sand, gravel, and fossils in the Red Crag Formation.  The white marks on the outer lip and interior of the aperture of the N. contraria specimen in the photo above show that the iron oxide did not penetrate into the substance of the shell, at least not this one.  Indeed, the stain scrapped off quite easily from the interior of this shell as I cleared out the matrix.

I am puzzled about one aspect of Lucy’s explanation, precisely how did (does?) the iron from the pyrite or the iron oxide saturate the Red Crag matrix?  Is Lucy asserting that the iron or iron oxide percolated vertically upward from the London Clay into the overlying Red Crag Formation?  It’s unclear from the photographs I’ve seen of the cliffs whether the coloring is more intense where the Clay and Crag are in direct contact and then fades as one moves up the cliffside.  (Have to travel there and see for myself.)

Perhaps the most far out aspect of this whole encounter with this Neptunea contraria fossil is what stares me in the face when I hold the fossil with the aperture toward me and the apex pointed up – the aperture is on the left.  The N. contraria is left-handed or sinistral.

Evolutionary biologist Geerat J. Vermeij notes that left-handedness is a rare species-level characteristic among gastropods, particularly marine gastropod species.  (The Geography of Evolutionary Opportunity:  Hypothesis and Two Cases in Gastropods, Integrative and Comparative Biology, Volume 42, Number 5, 2002.)

Left-handed coiling in gastropods poses a fascinating problem.  On the one hand, according to Vermeij, left-handedness is “unlikely to have significant survival-related benefits.”  In essence, it is “apparently functionless.”  On the other hand, it may have a marginally negative impact.  Research on sinistral members of otherwise dextral species has shown that they may be at some slight disadvantage relative to their dextral brethren (Stephen Jay Gould, et al., Consequences of Being Different:  Sinistral Coiling in Cerion, Evolution, Volume 39, Number 6, November, 1985).  So, Vermeij considers the circumstances under which a “functionless” trait with some slight deleterious effects might actually arise as a species-level characteristic.  He concludes that such a trait might emerge in environments “where resources are abundant” but “where predator-induced selection is weak.”  Intensive predator selection would, presumably, magnify the consequences of the adverse effects of sinistral coiling, explaining its rarity.

More recent research suggests that sinistral coiling in snails may in fact offer some advantages, at least relative to predation by crabs.  Crabs are typically right-handed and apparently have some difficulty managing the process of stripping left-handed snails of their shells.  That begs the question of why more gastropod species aren’t sinistral as a result of this advantage.  Paleontologist Gregory P. Dietl and Jonathan R. Hendricks suggest that perhaps this is an instance of sexual selection and natural selection working to offset each other.  But, ultimately, they throw up their hands and quote biologist and mathematician D’Arcy Wentworth Thompson, who wrote in 1943,
But why, in the general run of shells, all the world over, in the past and in the present, one direction of twist is so overwhelmingly commoner than the other, no man knows.
(As quoted by Dietl and Hendricks in their article titled Crab Scars Reveal Survival Advantage of Left-Handed Snails, Biology Letters, published online on March 21, 2006.)

That left-handedness among gastropods struck early naturalists as something unusual, if not literally a mistake, is evident by the names given some of these sinistral species.  Neptunea contraria is fairly mild – contraria means opposite or contrary in Latin.  But then there is the whelk whose left-handedness earned it the name Busycon perversum (Linnaeus, 1758).  Linnaeus originally named it Murex perversus.  Perversum is Latin for perverse, perverted, crooked, or wrong.

Speaking of which, the earliest description I have found of the Neptunea contraria is in Samuel Dale’s The History and Antiquities of Harwich and Dovercourt, Topographical, Dynastical and Political published in 1730.  Here he compares members of this species to those of a similar species that coils to the right:
They are like the precedent [the ones previously described] in all things excepting in the wrong Turn.  (p. 287, capitalization in the original)
A wrong turn.  A nicely unscientific assessment for a snail that, to these early naturalists, seemed to have come (had the expression been around then) out of left field.

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