Counter slab

Counter slab and slab, more often called a part and counter part in paleoentomology^[1] and paleobotany,^[2] are the matching halves of a compression fossil, a fossil-bearing matrix formed in sedimentary deposits. When excavated the matrix may be split along the natural grain or cleavage of the rock. A fossil embedded in the sediment may then also split down the middle, with fossil remains sticking to both surfaces, or the counter slab may simply show a negative impression or mould of the fossil.^[3] Comparing slab and counter slab has led to the exposure of a number of fossil forgeries.

Differences between the impressions on slab and counterslab led Fred Hoyle and Lee Spetner in 1985 to declare that some Archaeopteryx fossils had been forged, a claim dismissed by most palaeontologists.^[4]

In its November 1999 edition, National Geographic magazine announced the discovery of Archaeoraptor, a link between dinosaurs and birds, from a 125 million year-old fossil that had come from the Liaoning Province of China. Chinese palaeontologist Xu Xing came into possession of the counter slab through a fossil hunter. On comparing his fossil with images of Archaeoraptor it became evident that it was a composite fake. His note to National Geographic led to consternation and embarrassment. A certain Lewis Simons investigated the matter on behalf of National Geographic. In October 2000 he reported what he termed:

"... a tale of misguided secrecy and misplaced confidence, of rampant egos clashing, self-aggrandizement, wishful thinking, naïve assumptions, human error, stubbornness, manipulation, backbiting, lying, corruption, and, most of all, abysmal communication. "

It was eventually determined that Archaeoraptor had been constructed from parts of an Early Cretaceous bird Yanornis martini and a small dinosaur Microraptor zhaoianus^[5]

In order to increase their profit, fossil hunters and dealers occasionally sell slab and counter slab separately. A reptile fossil also found in Liaoning Province was described and named Sinohydrosaurus in 1999 by the Beijing Natural History Museum. In the same year the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing described and named Hyphalosaurus lingyuanensis, unaware they were working with the counter slab of the same specimen. Hyphalosaurus is now the accepted name.^[6]

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