Wooster’s Fossils of the Week: An Ordovician hardground with a bryozoan and borings — and an unexpected twist

August 1st, 2014

1 Hardground Bryo Large 071514aThe view above, one quite familiar to me, is of a carbonate hardground from the Upper Ordovician Grant Lake Formation exposed near Washington, Mason County, Kentucky. We are looking directly at the bedding plane of this limestone. The lumpy, spotted fossil covering about half the surface is a trepostome bryozoan. It looks like a dollop of thick pudding plopped on the rock. In the upper left are round holes that are openings of the trace fossil Trypanites, a common boring in carbonate hard substrates.
2 Closer hdgd bryo 071514bThis closer view shows the bryozoan details in the right half. You can barely pick out the tiny pin holes of the zooecia (the tubes that contained the individual zooids) and see the raised areas called maculae, which may have assisted in directing water currents for these colonial filter-feeders. Without a thin-section or peel I can’t identify the bryozoan beyond trepostome, but I suspect it is Amplexopora. The Trypanites borings in the hardground surface are also visible.
3 Hardground oblique Ordovician sm 071514cThis oblique view brings all the elements together. The bryozoan has closely encrusted the microtopography of the hardground surface. The Trypanites borings are shown cutting directly through the limestone of the hardground. Both of these observations confirm that the hardground was cemented seafloor sediment when the encrusters and borers occupied it.
4 Cross section hdgd 071514dHere is a full cross-section view showing the borings and the draping nature of the bryozoan. Now for the twist — I’m showing the specimen upside-down! It was actually found in place with the bryozoan down, not up. This is the roof of a small cave on the Ordovician seafloor. The bryozoan was hanging down from the ceiling, and the boring organisms were drilling upwards. The true orientation of this specimen is thus —
5 Cross section hdgd right side up 071514dThe cave was apparently formed after the carbonate hardground was cemented on the seafloor. Currents may have washed away unconsolidated muds underneath the hardground, forming a small cavity then occupied by the borers and the bryozoan: an ancient cave fauna. Brett & Liddell (1978) showed similar cavity encrustation in the Middle Ordovician, and I recorded a nearly identical situation in the Middle Jurassic of Utah (Wilson, 1998). Other detailed fossil marine caves are described from the Jurassic by Palmer & Fürsich (1974) and Taylor & Palmer (1994).

I should write up this Ordovician story someday!

References:

Brett, C.E. and Liddell, W.D. 1978. Preservation and paleoecology of a Middle Ordovician hardground community. Paleobiology 4: 329– 348.

Bromley, R.G. 1972. On some ichnotaxa in hard substrates, with a redefinition of Trypanites Mägdefrau. Paläontologische Zeitschrift 46: 93–98.

Palmer, T.J. 1982. Cambrian to Cretaceous changes in hardground communities. Lethaia 15: 309–323.

Palmer, T.J. and Fürsich, F.T. 1974. The ecology of a Middle Jurassic hardground and crevice fauna. Palaeontology 17: 507–524.

Taylor, P.D. and Palmer, T.J. 1994. Submarine caves in a Jurassic reef (La Rochelle, France) and the evolution of cave biotas. Naturwissenschaften 81: 357-360.

Taylor, P.D. and Wilson. M.A. 2003. Palaeoecology and evolution of marine hard substrate communities. Earth-Science Reviews 62: 1–103.

Wilson, M.A. 1998. Succession in a Jurassic marine cavity community and the evolution of cryptic marine faunas. Geology 26: 379-381.

Wilson, M.A. and Palmer, T.J. 1992. Hardgrounds and hardground faunas. University of Wales, Aberystwyth, Institute of Earth Studies Publications 9: 1–131.

Wooster’s Fossil of the Week: A faulted oyster ball from the Middle Jurassic of Utah

July 25th, 2014

Split oyster ball 062914I’m returning this week to one of my favorite fossil types: the ostreolith, popularly known as the “oyster ball”. These were lovingly described in a previous blog entry, so please click there to see how they were formed and some additional images. They are found almost exclusively in the Carmel Formation (Middle Jurassic) of southwestern Utah.They are circumrotatory (a fancy word for “rolling around while forming”) accumulations of small cup-like oysters along with minor numbers of plicatulid bivalves, disciniscid brachiopods, cyclostome bryozoans (see Taylor & Wilson, 1999), and mytilid bivalves that drilled borings known as Gastrochaenolites. They are nice little hard-substrate communities originally nucleated on bivalve shells (Wilson et al., 1998).

oyster ball close 062914Here is a close view of the oyster valves on the outside of the ostreolith. They are attached to similar valves below them, and it is oysters all the way to the center.

What is special about our specimen here is that it managed to obtain a fault right through its center! The chances of this happening are slim, given that they are relatively rare in the rock matrix. The faulting was probably during the Miocene related to a “left-lateral transfer zone that displaces north-south–trending crustal blocks of the eastern Basin and Range Province to the west” (Petronis et al., 2014, p. 534). This is an interesting tectonic region between the Basin and Range Province and the Colorado Plateau.

Slickenfibers 062914A close view of the fault surface shows it is a striated slickenside. The striations (called slickenlines) are parallel to the direction of movement, not that we have to guess when we look at the ostreolith itself. There are also calcitic deposits here formed during faulting called slickenfibres. These elongated crystals have tiny step-like breaks in them that show the actual direction of movement.

Another nice specimen combining paleontology and structural geology.

References:

Petronis, M.S., Holm, D.K., Geissman, J.W., Hacker, D.B. and Arnold, B.J. 2014. Paleomagnetic results from the eastern Caliente-Enterprise zone, southwestern Utah: Implications for initiation of a major Miocene transfer zone. Geosphere 10: 534-563.

Taylor, P.D. and Wilson, M.A. 1999. Middle Jurassic bryozoans from the Carmel Formation of southwestern Utah. Journal of Paleontology 73: 816-830.

Wilson, M.A., Ozanne, C.R. and Palmer, T.J. 1998. Origin and paleoecology of free-rolling oyster accumulations (ostreoliths) in the Middle Jurassic of southwestern Utah, USA. Palaios 13: 70-78.

Wooster’s Fossils of the Week: Silicified productid brachiopods from the Permian of West Texas

July 18th, 2014

Productids ventral valves 052514The three beauties above are productid brachiopods from the Road Canyon Formation (Middle Permian, Roadian, approximately 270 million years old) in the Glass Mountains of southwestern Texas. They are part of a series we’ve done on the silicified fauna of a block of limestone we dissolved in the lab many years ago. The calcitic shells have been replaced with silica during the process of fossilization, so they can be extracted from the carbonate matrix with hydrochloric acid. This is a primary way we can see delicate parts of a fossil, like the long hollow spines above. Ordinarily these would have been lost under the usual processes of taphonomy.

The specimens are highly convex ventral valves, which are characteristic of the productid brachiopods. The long hollow spines helped distribute the weight of these brachiopods on soft and unstable substrata, like a sandy or muddy sediment. This is often called “the snowshoe effect”. Below is a diagram reconstructing productid brachiopods on a sandy substrate with their spines keeping them from sinking below the sediment-water interface.

productid diagramProductid Permian Texas 585Here is a closer view of the ventral valve exterior of one of these productid brachiopods. You can see how delicate the hollow spines are.

Productid interior ventral Permian Texas 585This is the interior of the same valve. Each spine has a hole connecting it to the inside of the shell. The mantle, which secretes the shell and has other physiological functions, extended out into each spine to build its length and possibly carry some sort of sensory abilities.

I have been unable to identify these brachiopods because of the bewilderingly large number of them described by Cooper and Grant in the 1960s and 1970s. Maybe one of our readers can give it a shot!

References:

Brunton, C.H.C., Lazarev, S.S. and Grant, R.E. 1995. A review and new classification of the brachiopod order Productida. Palaeontology 38: 915-936.

Cooper, G.A., and Grant, R.E., 1964, New Permian stratigraphic units in Glass Mountains, West Texas. American Association of Petroleum Geologists Bulletin 48: 1581-1588.

Cooper, G.A., and Grant, R.E. 1966. Permian rock units in the Glass Mountains, West Texas, In: Contributions to stratigraphy, 1966: U.S. Geological Survey Bulletin 1244-E: E1-E9.

Cooper, G.A. and Grant, R.E. 1972. Permian brachiopods of West Texas, I. Smithsonian Contributions to Paleobiology 14: 1–228. [and five other volumes]

Shiino, Y. and Suzuki, Y. 2007. Articulatory and musculatory systems in a Permian concavo-convex brachiopod Waagenoconcha imperfecta Prendergast, 1935 (Productida, Brachiopoda). Paleontological research 11: 265-275.

Wooster’s Fossils of the Week: Silicified chonetid brachiopods from the Permian of West Texas

July 11th, 2014

Dyoros planiextensus Cooper and Grant 1975 585Above are four valves of the chonetid brachiopod Dyoros planiextensus Cooper and Grant, 1975. They are preserved by silicification and were recovered from a block of the Road Canyon Formation (Roadian Stage of the Guadalupian Series of the Permian System) from the Glass Mountains of southwestern Texas. It is from the same unit and location as the rhynchonellid brachiopod presented two weeks ago in this blog. (Please see that entry for additional links and explanations of the preservation.)

It took me awhile to work out the systematics of this species, so I must show you in exquisite detail —

Phylum Brachiopoda
Class Strophomenata Williams et al., 1996
Order Productida Sarytcheva and Sokolskaya, 1959
Suborder Chonetidina Muir-Wood, 1955
Superfamily Chonetoidea Bronn, 1862
Family Rugosochonetidae Muir-Wood, 1962
Genus Dyoros Stehli 1954
Species Dyoros planiextensus Cooper and Grant, 1975

Like music!

The chonetid brachiopods (at the suborder level) can be extremely common in Permo-Carboniferous units. I’ve seen hillsides in southeastern Ohio that seemed coated with them as they eroded from the shales beneath. They were well adapted to living on soft sediments with their flat, thin shells. In life they had a series of small hollow spines extended from the hinge line (the straight parts of the shell where the valves articulated; top in the photos above) to help anchor them as juveniles and possibly serve as extensions of their sensory systems.

Just a short entry this week. If all proceeded by plan, I’m somewhere deep in China right now!

References:

Cooper, G.A. and Grant, R.E. 1975. Permian brachiopods of West Texas, III. Smithsonian Contributions to Paleobiology 19:795-1921.

Racheboeuf, P.R., Moore, T.E. and Blodgett, R.B. 2004. A new species of Dyoros (Brachiopoda; Chonetoidea) from Nevada (United States) and stratigraphic implications for the Pennsylvanian and Permian Antler Overlap assemblage. Geobios 37: 382-394.

Stehli, F.G. 1954. Lower Leonardian Brachiopoda of the Sierra Diablo. Bulletin of the American Museum of Natural History 105: 257-358.

Wooster’s Fossil of the Week: A barnacle and sponge symbiosis from the Middle Jurassic of Israel

July 4th, 2014

Barnacle boring bioclaustration 1

[Programing note: Wooster’s Fossil of the Week is now being released on Fridays to correspond with the popular Fossil Friday on Twitter and other platforms.]

This week’s fossil is again from the Matmor Formation (Middle Jurassic, Callovian) of southern Israel. (What can I say? We have a lot of them!) We are looking above at a crinoid pluricolumnal (a section of the stem made of several columnals) almost completely encrusted by a calcareous sponge (the sheet-like form with tiny pores). A round oyster is attached to the sponge in the lower center. In the left half you see the items of our interest this week: ovoid holes produced by barnacles. This specimen was studied by Lizzie Reinthal (’14) as part of her Senior Independent Study on the taphonomy of the Matmor crinoids.
Barnacle boring bioclaustration 2These barnacle holes are interesting because we can see in this closer view that the sponge grew around them. There is thickened sponge wall at the margins of the holes, and the feature in the middle is a thick mound built around one of these holes. The barnacles in the holes and the sponge were living together. If they weren’t either the sponge would have overgrown the empty holes or the barnacle would have cut through the dead sponge skeleton. This is an example of symbiosis. It would be a facultative relationship because the sponge and barnacle did not need each other to survive; each does just fine without the other. It could be considered parasitic if the barnacles acquired nutrients the sponge would have ordinarily received, or vice versa.
Barnacle boring bioclaustration 3This third view is of the edge of the sponge skeleton as it partially overlaps the barnacle holes. Now we see the nature of the intergrowth. The barnacle holes are actually borings into the crinoid pluricolumnal below. They are the trace fossil called Rogerella, which we have seen before in this blog. The sponge grew along the crinoid substrate covering all sorts of small holes, cracks and crevices, but when it reached these borings living barnacles were still in them filter-feeding away with their filamentous legs. The sponge thus laid its skeleton right up to the hole edges, eventually surrounding them with their spongy matrix.

The holes are borings, a kind of trace fossil. The structure created when the sponge surrounds a living boring barnacle like this is more difficult to name. It is not technically a bioimmuration (see Taylor, 1990) because the barnacles were not passively subsumed within the sponge skeleton. It may be a bioclaustration (Palmer and Wilson, 1988) because the sponge adapted its skeleton to isolate and surround the barnacle. I think we can at least say these are trace fossils in the ethological (behavioral) group called Impedichnia (Tapanila, 2005) because the barnacles acted as impediments, or limiting factors, to the growth of the sponge.

I love these examples of symbiosis in the fossil record, and the interesting debates about their interpretations.

References:

Cónsole‐Gonella, C. and Marquillas, R.A. 2014. Bioclaustration trace fossils in epeiric shallow marine stromatolites: the Cretaceous‐Palaeogene Yacoraite Formation, northwestern Argentina. Lethaia 47: 107-119.

Palmer, T.J. and Wilson, M.A. 1988. Parasitism of Ordovician bryozoans and the origin of pseudoborings. Palaeontology 31: 939–949.

Tapanila, L. 2005. Palaeoecology and diversity of endosymbionts in Palaeozoic marine invertebrates: Trace fossil evidence. Lethaia 38: 89–99.

Taylor, P.D. 1990. Preservation of soft-bodied and other organisms by bioimmuration: A review. Palaeontology 33: 1–17.

Vinn, O. and Mõtus, M.A. 2014. Symbiotic worms in biostromal stromatoporoids from the Ludfordian (Late Silurian) of Saaremaa, Estonia. GFF (in press).

Wilson, M.A., Palmer, T.J. and Taylor, P.D. 1994. Earliest preservation of soft-bodied fossils by epibiont bioimmuration: Upper Ordovician of Kentucky. Lethaia 27: 269–270.

Wooster’s Fossil of the Week: A silicified rhynchonellid brachiopod from the Permian of West Texas

June 22nd, 2014

Rhynchonellid crura Permian Texas 585Sometimes fossils can be more useful when broken than whole. Above is a much-abused rhynchonellid brachiopod from the Road Canyon Formation (Middle Permian, Roadian, about 270 million years old) found in the Glass Mountains of southwestern Texas. It is part of a set of silicified fossils we etched out of a block of limestone in the last century. The shell has been replaced with resistant silica, so it was easy to extract from the limestone matrix with a long bath in hydrochloric acid that dissolved the carbonate but left everything else. The fossils are like delicate little glass husks. We’ve featured them in this blog several times.

Update: Matt Clapham kindly corrected me in the comments, and it is worth repeating in the text: “It’s Stenoscisma. The large spoon-shaped projection is actually called a spondylium, formed from merged dental plates and it’s quite distinctive for the Stenoscismatidae. The crura are broken but still visible in your specimen; they are the little struts parallel to the narrowest part of the spondylium. There are five Stenoscisma species that appear common in the Road Canyon Formation and yours looks most similar to Stenoscisma triquetrum to me (weakly sulcate with ribs that are somewhat subtle but still extend near the beak).” I made a bonehead mistake labeling the spondylium incorreectly, hence the “c”. Here’s to the value of Twitter, blogging, and knowledgeable colleagues!
Rhynchonellid Permian Texas 585Here’s the dorsal side of the specimen for completion. The exterior is in poor shape.

I’d love to identify this specimen to at least the genus level [update: see above and the comments!], but there is not enough detail preserved, at least for my skill set. The Permian brachiopods of West Texas were famously studied by G. Arthur Cooper and Richard E. Grant in the 1960s and 1970s. The numbers of species are overwhelming in this ancient reef system, and almost all of them are preserved in this delicate way.

References:

Cooper, G.A., and Grant, R.E., 1964, New Permian stratigraphic units in Glass Mountains, West Texas. American Association of Petroleum Geologists Bulletin 48: 1581-1588.

Cooper, G.A., and Grant, R.E. 1966. Permian rock units in the Glass Mountains, West Texas, In: Contributions to stratigraphy, 1966: U.S. Geological Survey Bulletin 1244-E: E1-E9.

Cooper, G.A. and Grant, R.E. 1972. Permian brachiopods of West Texas, I. Smithsonian Contributions to Paleobiology 14: 1–228. [and five other volumes]

Olszewski, T.D. and Erwin, D.H. 2009. Change and stability in Permian brachiopod communities from western Texas. Palaios 24: 27-40.

Wooster’s Fossil of the Week: A geopetal structure in a boring from the Middle Jurassic of Israel

June 15th, 2014

Geopetal Structure 585We have a very simple trace and body fossil combination this week that provides a stratigraphic and structural geologic tool. Above is a bit of scleractinian coral from the Matmor Formation (Middle Jurassic, Callovian) of Makhtesh Gadol in southern Israel. The coral skeleton was originally made of aragonite. It has been since recrystallized into a coarse sparry calcite, so we can no longer see the internal skeletal details of the coral. In the middle of this polished cross-section is an elliptical hole. This is a boring made by a bivalve (the trace fossil Gastrochaenolites). Inside the boring you see a separate elliptical object: a cross-section of a bivalve shell. This could be the bivalve that made the boring or, more likely, a bivalve that later occupied the boring for a living refuge. This, then, is the trace fossil (Gastrochaenolites) and body fossil (the bivalve shell) juxtaposition.

That stratigraphic and structural interest is that the boring and the bivalve shell are partially filled with a yellow sediment. This sediment has gravitationally settled to the bottom of these cavities (at slightly different levels). These holes have thus acted as natural builders’ levels showing is which way was down and which was up at the time of deposition. We can tell without any clues from the recrystallized coral the “way up” before any later structural deformation (or in this case rolling around on the outcrop) changed the orientation of the coral. Pretty cool and simple, eh? The name for this feature is a geopetal structure. There are some faulted and folded sedimentary rock exposures in the world where we search diligently for these little clues to original orientation (see, for example, Klompmaker et al., 2013). Not all geopetal structures have fossil origins (i.e., Mozhen et al., 2010), but most do. A little gift from paleontology to its sister disciplines.

References:

Klompmaker, A.A., Ortiz, J.D. and Wells, N.A. 2013. How to explain a decapod crustacean diversity hotspot in a mid-Cretaceous coral reef. Palaeogeography, Palaeoclimatology, Palaeoecology 374: 256-273.
Mozhen, G., Chuanjiang, W., Guohui, Y., Xueqiang, S., Guohua, Z. and Xin, W. 2010. Features, origin and geological significance of geopetal structures in Carboniferous volcanic rocks in Niudong Block, Santanghu Basin. Marine Origin Petroleum Geology 3: 15.
Wieczorek, J. 1979. Geopetal structures as indicators of top and bottom. Annales de la Societé géologique de Pologne 49: 215-221.

Wooster’s Fossil of the Week: A fragment of an asteroid (the sea star kind) from the Upper Cretaceous of Israel

June 8th, 2014

zichor asteroid aboral 585This is not an important fossil — there is not enough preserved to put a name on it beyond Family Goniasteridae Forbes, 1841 (thanks, Dan Blake) — but it was a fun one to find. It also photographs well. This is a ray fragment of an asteroid (from the group commonly known as the sea stars or starfish) I picked up from the top meter of the Zichor Formation (Coniacian, Upper Cretaceous) in southern Israel (Locality C/W-051) on my field trip there in April 2014. We are looking at the aboral (or top) surface; below is the oral view.
zichor asteroid oral surface 585In this oral perspective you can see a group of tiny, jumbled plates running down the center. This is the ambulacrum, which in life had a row of tube feet extending out for locomotion and grasping prey.
asteroid 2004Above is a sea star held by my son Ted on Long Island, The Bahamas, back in 2004. You can see a bit of resemblance between this modern species and the Cretaceous fossil, mainly the  large knobby ossicles running down the periphery of the rays.

The asteroids have a poor fossil record, at least when compared to other echinoderms like crinoids and echinoids. It appears that all post-Paleozoic asteroids derive from a single ancestral group that squeaked through the Permian extinctions (Gale, 2013). There is a significant debate about the evolution of the asteroids (see Blake and Mah, 2014, for the latest). Unfortunately our little critter is not going to help much in its resolution.

Recently it has been discovered that some living asteroids have microlenses in their ossicles to provide a kind of all-surface photoreception ability. Gorzelak et al. (2014) have found evidence that some Cretaceous asteroids had similar photoreceptors. Maybe our fossil goniasterid fragment could yield this kind of secret property with closer examination.

References:

Blake, D.B. and Mah, C.L. 2014. Comments on “The phylogeny of post-Palaeozoic Asteroidea (Neoasteroidea, Echinodermata)” by AS Gale and perspectives on the systematics of the Asteroidea. Zootaxa 3779: 177-194.

Gale, A.S. 2011. The phylogeny of post-Paleozoic Asteroidea (Neoasteroidea, Echinodermata). Special Papers in Palaeontology 38, 112 pp.

Gale, A.S. 2013. Phylogeny of the Asteroidea, p. 3-14. In: Lawrence, J.M. (ed.), Starfish: Biology and Ecology of the Asteroidea. The Johns Hopkins University Press, Baltimore.

Gorzelak, P., Salamon, M.A., Lach, R., Loba, M. and Ferré, B. 2014. Microlens arrays in the complex visual system of Cretaceous echinoderms. Nature Communications 5, Article 3576, doi:10.1038/ncomms4576.

Loriol, P. de. 1908. Note sur quelques stellérides du Santonien d’Abou-Roach. Bulletin de l’Institut égyptien 2: 169-184.

Mah, C.L. and Blake, D.B. 2012. Global diversity and phylogeny of the Asteroidea (Echinodermata). PLOS ONE 7(4), e35644.

Wooster’s Fossil of the Week: My favorite part of a crinoid (Middle Jurassic of Israel)

June 1st, 2014

Apiocrinites negevensis proximale 585In April of this year I completed my 11th trip to southern Israel for fieldwork in the Mesozoic. My heart warmed every time I saw these robust plates of the crinoid Apiocrinities negevensis, which was reviewed in a previous blog post. They are thick disks of calcite with a heft and symmetry like exotic coins. They are easy to spot in the field because of their size and incised perfect star. They have been a critical part of our paleoecological and systematic studies of the Matmor Formation (Callovian, Middle Jurassic) in the Negev. Lizzie Reinthal (14) and Steph Bosch (14) know them particularly well!
negevensis proximales 1This part of the crinoid is called the proximale. It has a round base that articulates with the columnal below it in the stem, and its top has five facets that hold the basal plates of the calyx. It is thus the topmost columnal, specialized to serve as the integration between the articulated stem below and the complicated head above. The pentastellate (five-armed star, but you probably figured that out) impression is called the areola. In the very center is the open hole of the lumen, which goes from the head all the way down through the stem to the holdfast as an internal fluid-filled cavity.
Composite Miller Apiocrinites arrowedAbove are Miller’s (1821) original illustrations of Apiocrinites rotundus with the proximale shown by the red arrow. Note how thin this piece is compared to the equivalent from Apiocrinites negevensis. The significant thickness of the proximale is one of the distinguishing features of the Negev species.

I saw many more of these beautiful fossils in the field this year. We don’t need any more for our research, but they always indicate that other good fossils are nearby.

References:

Ausich, W.I. and Wilson, M.A. 2012. New Tethyan Apiocrinitidae (Crinoidea; Articulata) from the Jurassic of Israel. Journal of Paleontology 86: 1051-1055.

Miller, J.S. 1821. A natural history of the Crinoidea or lily-shaped animals, with observation on the genera Asterias, Euryale, Comatula, and Marsupites. Bryan & Co, Bristol, 150 pp.

Wilson, M.A., Feldman, H.R. and Krivicich, E.B. 2010. Bioerosion in an equatorial Middle Jurassic coral-sponge reef community (Callovian, Matmor Formation, southern Israel). Palaeogeography, Palaeoclimatology, Palaeoecology 289: 93-101.

Wooster’s Fossil of the Week: A fly in amber

May 25th, 2014

Fly in amber 012614A classic fossil this week. I wish I could say more about it. The specimen lost its label years ago, so I don’t know where it is from or its age (although a good guess is Neogene). I also can’t identify it with my skill set beyond “fly” (Order Diptera). Beautiful, though. The images were not easy to make. I used our photomicroscope and played with a combination of light from below (transmitted) and above (reflected). The polished amber fragment is about the size of a pea and the fly is near the middle of it.
Fly legs in amber 012614A closer view here of the legs. Each segment can be seen, along with their tiny spines. This seems to be a particularly long-legged fly.

Preservation in amber is a well known phenomenon. An insect like ours gets itself trapped in a drop of tree resin. The resin hardens into amber by losing much of its volatile content with heat over time. Polish the piece and you can peer inside and see the occasional treasures of three-dimensionally preserved organisms. Oddly enough, in most cases these fossils are hollow external molds with no internal tissues preserved. What we see is the outside of this cavity with pigments embedded in the amber. (This fly has gorgeous red eyes, for example.) Remember the Jurassic Park premise that dinosaur DNA had been recovered from blood in a mosquito’s belly preserved in Dominican amber? It just doesn’t happen. In fact, a recent study (Penney et al., 2013) showed that insect DNA doesn’t even survive in sub-fossil assemblages.

I know from experience that it is very easy to be fooled by fake amber. As a policy, I’ve learned to not buy it in an Estonian open market (just as an example!). After Jurassic Park appeared, the demand for amber shot up, especially if it had animals in it. Artificial amber, and amber made from shavings and fragments (“pressed amber”) flooded the market. Caveat emptor. I tested our piece and it passed.

For more images of insects in amber, please follow the link or just search “amber”.

References:

Penney, D. 2002. Paleoecology of Dominican amber preservation: spider (Araneae) inclusions demonstrate a bias for active, trunk-dwelling faunas. Paleobiology 28: 389-398.

Penney, D., Wadsworth, C., Fox, G., Kennedy, S.L., Preziosi, R.F. and Brown, T.A. 2013. Absence of ancient DNA in sub-fossil insect inclusions preserved in ‘Anthropocene’ Colombian copal. PloS one 8(9), e73150. DOI: 10.1371/journal.pone.0073150

Poinar Jr, G.O. 1993. Insects in amber. Annual Review of Entomology 38: 145-159.

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